Method and an apparatus for reproducing bitstream having non-sequential system clock data seamlessly therebetween

ABSTRACT

A system stream contiguous reproduction apparatus to which are input one or more system streams interleaving at least moving picture data and audio data, and system stream connection information includes a system clock STC generator for producing the system clock that is used as the system stream reproduction reference clock. The system stream contiguous reproduction apparatus further includes one or more signal processing decoders that operate referenced to the system clock STC, decoder buffers for temporarily storing the system stream data transferred to the corresponding signal processing decoders, and STC selectors for selecting a system clock STC referenced by the signal processing decoders when decoding the first system stream, and another system clock STC referenced by the signal processing decoders when decoding a second system stream reproduced contiguously to the first system stream.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and apparatus forseamlessly reproducing a bitstream having non-sequential system clockdata therein and, more specifically, to a bitstream for use in anauthoring system for variously processing a data bitstream comprisingthe video data, audio data, and sub-picture data constituting each ofplural program titles containing related video data, audio data, andsub-picture data content to generate a bitstream from which a new titlecontaining the content desired by the user can be reproduced, andefficiently recording and reproducing said generated bitstream using aparticular recording medium.

[0003] 2. Description of the Prior Art

[0004] Authoring systems used to produce program titles comprisingrelated video data, audio data, and sub-picture data by digitallyprocessing, for example, multimedia data comprising video, audio, andsub-picture data recorded to laser disk or video CD formats arecurrently available. Systems using Video-Cds in particular are able torecord video data to a CD format disk, which was originally designedwith an approximately 600 MB recording capacity for storing digitalaudio data only, by using such high efficiency video compressiontechniques as MPEG. As a result of the increased effective recordingcapacity achieved using data compression techniques, karaoke titles andother conventional laser disk applications are gradually beingtransferred to the video CD format.

[0005] Users today expect both sophisticated title content and highreproduction quality. To meet these expectations, each title must becomposed from bitstreams with an increasingly deep hierarchicalstructure. The data size of multimedia titles written with bitstreamshaving such deep hierarchical structures, however, is ten or more timesgreater than the data size of less complex titles. The need to editsmall image (title) details also makes it necessary to process andcontrol the bitstream using low order hierarchical data units.

[0006] It is therefore necessary to develop and prove a bitstreamstructure and an advanced digital processing method including bothrecording and reproduction capabilities whereby a large volume, multiplelevel hierarchical digital bitstream can be efficiently controlled ateach level of the hierarchy. Also needed are an apparatus for executingthis digital processing method, and a recording media to which thebitstream digitally processed by said apparatus can be efficientlyrecorded for storage and from which said recorded information can bequickly reproduced.

[0007] Means of increasing the storage capacity of conventional opticaldisks have been widely researched to address the recording medium aspectof this problem. One way to increase the storage capacity of the opticaldisk is to reduce the spot diameter D of the optical (laser) beam. Ifthe wavelength of the laser beam is l and the aperture of the objectivelens is NA, then the spot diameter D is proportional to l/NA, and thestorage capacity can be efficiently improved by decreasing l andincreasing NA.

[0008] As described, for example, in U.S. Pat. No. 5,235,581, however,coma caused by a relative tilt between the disk surface and the opticalaxis of the laser beam (hereafter “tilt”) increases when a largeaperture (high NA) lens is used. To prevent tilt-induced coma, thetransparent substrate must be made very thin. The problem is that themechanical strength of the disk is low when the transparent substrate isvery thin.

[0009] MPEG1, the conventional method of recording and reproducingvideo, audio, and graphic signal data, has also been replaced by themore robust MPEG2 method, which can transfer large data volumes at ahigher rate. It should be noted that the compression method and dataformat of the MPEG2 standard differ somewhat from those of MPEG1. Thespecific content of and differences between MPEG1 and MPEG2 aredescribed in detail in the ISO-11172 and ISO-13818 MPEG standards, andfurther description thereof is omitted below.

[0010] Note, however, that while the structure of the encoded videostream is defined in the MPEG2 specification, the hierarchical structureof the system stream and the method of processing lower hierarchicallevels are not defined.

[0011] As described above, it is therefore not possible in aconventional authoring system to process a large data stream containingsufficient information to satisfy many different user requirements.Moreover, even if such a processing method were available, the processeddata recorded thereto cannot be repeatedly used to reduce dataredundancy because there is no large capacity recording medium currentlyavailable that can efficiently record and reproduce high volumebitstreams such as described above.

[0012] More specifically, particular significant hardware and softwarerequirements must be satisfied in order to process a bitstream using adata unit smaller than the title. These specific hardware requirementsinclude significantly increasing the storage capacity of the recordingmedium and increasing the speed of digital processing; softwarerequirements include inventing an advanced digital processing methodincluding a sophisticated data structure.

[0013] Therefore, the object of the present invention is to provide aneffective authoring system for controlling a multimedia data bitstreamwith advanced hardware and software requirements using a data unitsmaller than the title to better address advanced user requirements.

[0014] To share data between plural titles and thereby efficientlyutilize optical disk capacity, multi-scene control whereby scene datacommon to plural titles and the desired scenes on the same time-basefrom within multiscene periods containing plural scenes unique toparticular reproduction paths can be freely selected and reproduced isdesirable.

[0015] However, when plural scenes unique to a reproduction path withinthe multi-scene period are arranged on the same time-base, the scenedata must be contiguous. Unselected multi-scene data is thereforeunavoidably inserted between the selected common scene data and theselected multi-scene data. The problem this creates when reproducingmulti-scene data is that reproduction is interrupted by this unselectedscene data.

[0016] In other words, except when a VOB, which is normally asingle-stream title editing unit, is divided into discrete, streams,seamless reproduction cannot be achieved by simply connecting andreproducing individual VOB. This is because while the reproduction ofvideo, audio, and sub-picture streams forming each VOB must besynchronized, the means for achieving this synchronization is enclosedin each VOB. As a result, the synchronization means will not functionnormally at VOB connections if the VOB are simply connected together.

[0017] The object of the present invention is therefore to provide areproduction apparatus enabling seamless reproduction whereby scene datacan be reproduced without intermittence even from these multi-sceneperiods.

[0018] The object of the present invention is therefore to provide anoptical disk medium from which data can be seamlessly reproduced withoutaudio or video intermitting even in such multi-scene periods, andreproducing apparatus implementing said recording and reproducingmethod.

[0019] The present application is based upon Japanese Patent ApplicationNo. 7-276710 and 8-041583, which were filed on Sep. 29, 1995 and Feb.28, 1996, respectively, the entire contents of which are expresslyincorporated by reference herein.

SUMMARY OF THE INVENTION

[0020] The present invention has been developed with a view tosubstantially solving the above described disadvantages and has for itsessential object to provide an improved method and apparatus forreproducing bitstream having non-sequential system clock data seamlesslytherebetween.

[0021] In order to achieve the aforementioned objective, a system streamcontiguous reproduction apparatus to which are input one or more systemstreams interleaving at least moving picture data and audio data, andsystem stream connection information comprises a system clock STCgenerator for producing the system clockthat is used as the systemstream reproduction reference clock, one or more signal processingdecoders that operate referenced to the system clock STC, decoderbuffers for temporarily storing the system stream data transferred tothe corresponding signal processing decoders, and STC selectors forselecting a system clock STC referenced by the signal processingdecoders when decoding the first system stream, and another system clockSTC referenced by the signal processing decoders when decoding a secondsystem stream reproduced contiguously to the first system stream.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] These and other objects and features of the present inventionwill become clear from the following description taken in conjunctionwith the preferred embodiments thereof with reference to theaccompanying drawings throughout which like parts are designated by likereference numerals, and in which:

[0023]FIG. 1 is a graph schematically showing a structure of multi mediabit stream according to the present invention,

[0024]FIG. 2 is a block diagram showing an authoring encoder accordingto the present invention,

[0025]FIG. 3 is a block diagram showing an authoring decoder accordingto the present invention,

[0026]FIG. 4 is a side view of an optical disk storing the multi mediabit stream of FIG. 1,

[0027]FIG. 5 is an enlarged view showing a portion confined by a circleof FIG. 4,

[0028]FIG. 6 is an enlarged view showing a portion confined by a circleof FIG. 5,

[0029]FIG. 7 is a side view showing a variation of the optical disk ofFIG. 4,

[0030]FIG. 8 is a side view showing another variation of the opticaldisk of FIG. 4,

[0031]FIG. 9 is a plan view showing one example of track path formed onthe recording surface of the optical disk of FIG. 4,

[0032]FIG. 10 is a plan view showing another example of track pathformed on the recording surface of the optical disk of FIG. 4,

[0033]FIG. 11 is a diagonal view schematically showing one example of atrack path pattern formed on the optical disk of FIG. 7,

[0034]FIG. 12 is a plan view showing another example of track pathformed on the recording surface of the optical disk of FIG. 7,

[0035]FIG. 13 is a diagonal view schematically showing one example of atrack path pattern formed on the optical disk of FIG. 8,

[0036]FIG. 14 is a plan view showing another example of track pathformed on the recording surface of the optical disk of FIG. 8,

[0037]FIG. 15 is a graph in assistance of explaining a concept ofparental control according to the present invention,

[0038]FIG. 16 is a graph schematically showing the structure ofmultimedia bit stream for use in Digital Video Disk system according tothe present invention,

[0039]FIG. 17 is a graph schematically showing the encoded video streamaccording to the present invention,

[0040]FIG. 18 is a graph schematically showing an internal structure ofa video zone of FIG. 16.

[0041]FIG. 19 is a graph schematically showing the stream managementinformation according to the present invention,

[0042]FIG. 20 is a graph schematically showing the structure thenavigation pack NV of FIG. 17,

[0043]FIG. 21 is a graph is assistance of explaining a concept ofparental lock playback control according to the present invention,

[0044]FIG. 22 is a graph schematically showing the data structure usedin a digital video disk system according to the present invention,

[0045]FIG. 23 is a graph in assistance of explaining a concept ofMulti-angle scene control according to the present invention,

[0046]FIG. 24 is a graph in assistance of explaining a concept of multiscene data connection,

[0047]FIG. 25 is a block diagram showing a DVD encoder according to thepresent invention,

[0048]FIG. 26 is a block diagram showing a DVD decoder according to thepresent invention,

[0049]FIG. 27 is a graph schematically showing an encoding informationtable generated by the encoding system controller of FIG. 25,

[0050]FIG. 28 is a graph schematically showing an encoding informationtables,

[0051]FIG. 29 is a graph schematically showing an encoding parametersused by the video encoder of FIG. 25,

[0052]FIG. 30 is a graph schematically showing an example of thecontents of the program chain information according to the presentinvention,

[0053]FIG. 31 is a graph schematically showing another example of thecontents of the program chain information according to the presentinvention,

[0054]FIG. 32 is a block diagram showing a synchronizer of FIG. 26according to the present invention,

[0055]FIG. 33 is a graph in assistance of explaining a concept ofmulti-angle scene control according to the present in invention,

[0056]FIG. 34 is a flow chart, formed by FIGS. 34A and 34B, showing anoperation of the DVD encoder of FIG. 25,

[0057]FIG. 35 is a flow chart showing detailed of the encode-parameterproduction sub-routine of FIG. 34,

[0058]FIG. 36 is a flow chart showing the detailed of the VOB datasetting routine of FIG. 35,

[0059]FIG. 37 is a flow chart showing the encode parameters generatingoperation for a seamless switching,

[0060]FIG. 38 is a flow chart showing the encode parameters generatingoperation for a system stream,

[0061]FIG. 39 is a block diagram showing the STC generator of FIG. 32,

[0062]FIG. 40 is a graph in assistance of explaining the realtionshipthe relationship between the SCR, APTS, VDTS, and VPTS values,

[0063]FIG. 41 is a block diagram showing a modification of thesynchronizer of FIG. 32,

[0064]FIG. 42 is a block diagram showing a synchronization controller ofFIG. 41,

[0065]FIG. 43 is a flow chart showing an operation of the syncronizationcontroller of FIG. 42,

[0066]FIG. 44 is a graph in assistance of explaining the relationshipbetween the system clock reference SCR, the audio playback starting timeinformation APTS, the decoder reference clock STC, and the videoplayback starting time VPTS,

[0067]FIG. 45 is a graph in assistance of explaining the relationshipbetween the recording positions and values of SCR, APTS, and VPTS whenVOB #1 and VOB #2 are seamlessly reproduced,

[0068]FIG. 46 is a graph in assitance of explaining the relationshipbetween the. SCR, APTS, and VPTS values and recording positions in eachVOB,

[0069]FIG. 47 is a graph in assistance of explaining the relationshipbetween the SCR, APTS, and VPTS values and recording positions in theVOB,

[0070]FIG. 48 is a graph showing a time line from input of the VOB inFIG. 47 to the system decoder to output of the last audio and videoreproduction data,

[0071]FIG. 49 is a flow chart showing the operation of the DVD encoderof FIG. 26,

[0072]FIG. 50 is a flow chart showing details of the multi-anglenon-seamless switching control routine of FIG. 49,

[0073]FIG. 51 is a flow chart showing details of the multi-angleseamless switching control routine of FIG. 49,

[0074]FIG. 52 is a flow chart showing details of the parental locksub-routine of FIG. 49,

[0075]FIG. 53 is a flow chart showing details of the single scenesubroutine of FIG. 49,

[0076]FIGS. 54 and 55 are graphs showing decoding information tableproduced by the decoding system controller of FIG. 26,

[0077]FIG. 56 is a flow chart showing the operation of the DVD decoderDCD of FIG. 26,

[0078]FIG. 57 is a flow chart showing details of reproduction extractedPGC routing of FIG. 56,

[0079]FIG. 58 is a flow chart showing details of decoding data processof FIG. 57, performed by the stream buffer,

[0080]FIG. 59 is a flow chart showing details of the decodersynchronization process of FIG. 58,

[0081]FIG. 60 is a flow chart showing an during non-seamlessreproduction operation of the STC selection controller of FIG. 59,

[0082]FIG. 61 is a flow chart showing the operation of the STC selectioncontroller of FIG. 39 during seamless reproduction operation,

[0083]FIG. 62 is a flow chart showing the data transfering operation ofFIG. 57,

[0084]FIG. 63 is a flow chart showing details of the non multi-angledecoding process of FIG. 62,

[0085]FIG. 64 is a flow chart showing details of the non-multi-angledinterleave process of FIG. 63,

[0086]FIG. 65 is a flow chart showing details of the non-multi-angledcontiguous block process of FIG. 63,

[0087]FIG. 66 is a flow chart showing an modification of FIG. 63,

[0088]FIG. 67 is a flow chart showing details of the seamlessmulti-angle decoding process of FIG. 62,

[0089]FIG. 68 is a flow chart showing details of non-seamlessmulti-angle decoding process of FIG. 62,

[0090]FIG. 69 is a block diagram showing details of the stream buffer ofFIG. 26,

[0091]FIG. 70 is a flow chart showing the encode parameters generatingoperation for a system stream containing a single scene,

[0092]FIG. 71 is a graph schematically showing an actual arrangement ofdata blocks recorded to a data recording track on a recording mediumaccording to the present invention,

[0093]FIG. 72 is a graph schematically showing contiguous block regionsand interleaved block regions array,

[0094]FIG. 73 is a graph schematically showing a content of a VTS titleVOBS according to the present invention, and

[0095]FIG. 74 is a graph schematically showing an internal datastructure of the interleaved block regions according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0096] Data Structure of the Authoring System

[0097] The logic structure of the multimedia data bitstream processedusing the recording apparatus, recording medium, reproduction apparatus,and authoring system according to the present invention is describedfirst below with reference to FIG. 1.

[0098] In this structure, one title refers to the combination of videoand audio data expressing program content recognized by a user foreducation, entertainment, or other purpose. Referenced to a motionpicture (movie), one title may correspond to the content of an entiremovie, or to just one scene within said movie.

[0099] A video title set (VTS) comprises the bitstream data containingthe information for a specific number of titles. More specifically, eachVTS comprises the video, audio, and other reproduction data representingthe content of each title in the set, and control data for controllingthe content data.

[0100] The video zone VZ is the video data unit processed by theauthoring system, and comprises a specific number of video title sets.More specifically, each video zone is a linear sequence of K+1 videotitle sets numbered VTS #0-VTS #K where K is an integer value of zero orgreater. One video title set, preferably the first video title set VTS#0, is used as the video manager describing the content information ofthe titles contained in each video title set.

[0101] The multimedia bitstream MBS is the largest control unit of themultimedia data bitstream handled by the authoring system of the presentinvention, and comprises plural video zones vz.

[0102] Authoring Encoder EC

[0103] A preferred embodiment of the authoring encoder EC according tothe present invention for generating a new multimedia bitstream MBS byre-encoding the original multimedia bitstream MBS according to thescenario desired by the user is shown in FIG. 2. Note that the originalmultimedia bitstream MBS comprises a video stream St1 containing thevideo information, a sub-picture stream St3 containing caption text andother auxiliary video information, and the audio stream St5 containingthe audio information.

[0104] The video and audio streams are the bitstreams containing thevideo and audio information obtained from the source within a particularperiod of time. The sub-picture stream is a bitstream containingmomentary video information relevant to a particular scene. Thesub-picture data encoded to a single scene may be captured to videomemory and displayed continuously from the video memory for pluralscenes as may be necessary.

[0105] When this multimedia source data St1, St3, and St5 is obtainedfrom a live broadcast, the video and audio signals are supplied inreal-time from a video camera or other imaging source; when themultimedia source data is reproduced from a video tape or otherrecording medium, the audio and video signals are not real-time signals.

[0106] While the multimedia source stream is shown in FIG. 2 ascomprising these three source signals, this is for convenience only, andit should be noted that the multimedia source stream may contain morethan three types of source signals, and may contain source data fordifferent titles. Multimedia source data with audio, video, andsub-picture data for plural titles are referred to below as multi-titlestreams.

[0107] As shown in FIG. 2, the authoring encoder EC comprises a scenarioeditor 100, encoding system controller 200, video encoder 300, videostream buffer 400, sub-picture encoder 500, sub-picture stream buffer600, audio encoder 700, audio stream buffer 800, system encoder 900,video zone formatter 1300, recorder 1200, and recording medium M.

[0108] The video zone formatter 1300 comprises video object (VOB) buffer1000, formatter 1100, and volume and file structure formatter 1400.

[0109] The bitstream encoded by the authoring encoder EC of the presentembodiment is recorded by way of example only to an optical disk.

[0110] The scenario editor 100 of the authoring encoder EC outputs thescenario data, i.e., the user-defined editing instructions. The scenariodata controls editing the corresponding parts of the multimediabitstream MBS according to the user's manipulation of the video,sub-picture, and audio components of the original multimedia title. Thisscenario editor 100 preferably comprises a display, speaker(s),keyboard, CPU, and source stream buffer. The scenario editor 100 isconnected to an external multimedia bitstream source from which themultimedia source data St1, St3, and St5 are supplied.

[0111] The user is thus able to reproduce the video and audio componentsof the multimedia source data using the display and speaker to confirmthe content of the generated title. The user is then able to edit thetitle content according to the desired scenario using the keyboard,mouse, and other command input devices while confirming the content ofthe title on the display and speakers. The result of this multimediadata manipulation is the scenario data St7.

[0112] The scenario data St7 is basically a set of instructionsdescribing what source data is selected from all or a subset of thesource data containing plural titles within a defined time period, andhow the selected source data is reassembled to reproduce the scenario(sequence) intended by the user. Based on the instructions receivedthrough the keyboard or other control device, the CPU codes theposition, length, and the relative time-based positions of the editedparts of the respective multimedia source data streams St1, St3, and St5to generate the scenario data St7.

[0113] The source stream buffer has a specific capacity, and is used todelay the multimedia source data streams St1, St3, and St5 a known timeTd and then output streams St1, St3, and St5.

[0114] This delay is required for synchronization with the editorencoding process. More specifically, when data encoding and usergeneration of scenario data St7 are executed simultaneously, i.e., whenencoding immediately follows editing, time Td is required to determinethe content of the multimedia source data editing process based on thescenario data St7 as will be described further below. As a result, themultimedia source data must be delayed by time Td to synchronize theediting process during the actual encoding operation. Because this delaytime Td is limited to the time required to synchronize the operation ofthe various system components in the case of sequential editing asdescribed above, the source stream buffer is normally achieved by meansof a high speed storage medium such as semiconductor memory.

[0115] During batch editing in which all multimedia source data isencoded at once (“batch encoded”) after scenario data St7 is generatedfor the complete title, delay time Td must be long enough to process thecomplete title or longer. In this case, the source stream buffer may bea low speed, high capacity storage medium such as video tape, magneticdisk or optical disk.

[0116] The structure (type) of media used for the source stream buffermay therefore be determined according to the delay time Td required andthe allowable manufacturing cost.

[0117] The encoding system controller 200 is connected to the scenarioeditor 100 and receives the scenario data St7 therefrom. Based on thetime-base position and length information of the edit segment containedin the scenario data St7, the encoding system controller 200 generatesthe encoding parameter signals St9, St11, and St13 for encoding the editsegment of the multimedia source data. The encoding signals St9, St11,and St13 supply the parameters used for video, sub-picture, and audioencoding, including the encoding start and end timing. Note thatmultimedia source data St1, St3, and St5 are output after delay time Tdby the source stream buffer, and are therefore synchronized to encodingparameter signals St9, St11, and St13.

[0118] More specifically, encoding parameter signal St9 is the videoencoding signal specifying the encoding timing of video stream St1 toextract the encoding segment from the video stream St1 and generate thevideo encoding unit. Encoding parameter signal St11 is likewise thesub-picture stream encoding signal used to generate the sub-pictureencoding unit by specifying the encoding timing for sub-picture streamSt3. Encoding parameter signal St13 is the audio encoding signal used togenerate the audio encoding unit by specifying the encoding timing foraudio stream St5.

[0119] Based on the time-base relationship between the encoding segmentsof streams St1, St3, and St5 in the multimedia source data contained inscenario data St7, the encoding system controller 200 generates thetiming signals St21, St23, and St25 arranging the encodedmultimedia-encoded stream in the specified time-base relationship.

[0120] The encoding system controller 200 also generates thereproduction time information IT defining the reproduction time of thetitle editing unit (video object, VOB), and the stream encoding dataSt33 defining the system encode parameters for multiplexing the encodedmultimedia stream containing video, audio, and sub-picture data. Notethat the reproduction time information IT and stream encoding data St33are generated for the video object VOB of each title in one video zoneVZ.

[0121] The encoding system controller 200 also generates the titlesequence control signal St39, which declares the formatting parametersfor formatting the title editing units VOB of each of the streams in aparticular time-base relationship as a multimedia bitstream. Morespecifically, the title sequence control signal St39 is used to controlthe connections between the title editing units (VOB) of each title inthe multimedia bitstream MBS, or to control the sequence of theinterleaved title editing unit (VOBs) interleaving the title editingunits VOB of plural reproduction paths.

[0122] The video encoder 300 is connected to the source stream buffer ofthe scenario editor 100 and to the encoding system controller 200, andreceives therefrom the video stream St1 and video encoding parametersignal St9, respectively. Encoding parameters supplied by the videoencoding signal St9 include the encoding start and end timing, bit rate,the encoding conditions for the encoding start and end, and the materialtype. Possible material types include NTSC or PAL video signal, andtelecine converted material. Based on the video encoding parametersignal St9, the video encoder 300 encodes a specific part of the videostream St1 to generate the encoded video stream St15.

[0123] The sub-picture encoder 500 is similarly connected to the sourcestream buffer of the scenario editor 100 and to the encoding systemcontroller 200, and receives therefrom the sub-picture stream St3 andsub-picture encoding parameter signal St11, respectively. Based on thesub-picture encoding parameter signal St11, the sub-picture encoder 500encodes a specific part of the sub-picture stream St3 to generate theencoded sub-picture stream St17.

[0124] The audio encoder 700 is also connected to the source streambuffer of the scenario editor 100 and to the encoding system controller200, and receives therefrom the audio stream St5 and audio encodingparameter signal St13, which supplies the encoding start and end timing.Based on the audio encoding parameter signal St13, the audio encoder 700encodes a specific part of the audio stream St5 to generate the encodedaudio stream St19.

[0125] The video stream-buffer 400 is connected to the video encoder 300and to the encoding system controller 200. The video stream buffer 400stores the encoded video stream St15 input from the video encoder 300,and outputs the stored encoded video stream St15 as the time-delayedencoded video stream St27 based on the timing signal St21 supplied fromthe encoding system controller 200.

[0126] The sub-picture stream buffer 600 is similarly connected to thesub-picture encoder 500 and to the encoding system controller 200. Thesub-picture stream buffer 600 stores the encoded sub-picture stream St17output from the sub-picture encoder 500, and then outputs the storedencoded sub-picture stream St17 as time-delayed encoded sub-picturestream St29 based on the timing signal St23 supplied from the encodingsystem controller 200.

[0127] The audio stream buffer 800 is similarly connected to the audioencoder 700 and to the encoding system controller 200. The audio streambuffer 800 stores the encoded audio stream St19 input from the audioencoder 700, and then outputs the encoded audio stream St19 as thetime-delayed encoded audio stream St31 based on the timing signal St25supplied from the encoding system controller 200.

[0128] The system encoder 900 is connected to the video stream buffer400, sub-picture stream buffer 600, audio stream buffer 800, and theencoding system controller 200, and is respectively supplied therebywith the time-delayed encoded video stream St27, time-delayed encodedsub-picture stream St29, time-delayed encoded audio stream St31, and thestream encoding data St33. Note that the system encoder 900 is amultiplexer that multiplexes the time-delayed streams St27, St29, andSt31 based on the stream encoding data St33 (timing signal) to generatetitle editing unit (VOB) St35. The stream encoding data St33 containsthe system encoding parameters, including the encoding start and endtiming.

[0129] The video zone formatter 1300 is connected to the system encoder900 and the encoding system controller 200 from which the title editingunit (VOB) St35 and title sequence control signal St39 (timing signal)are respectively supplied. The title sequence control signal St39contains the formatting start and end timing, and the formattingparameters used to generate (format) a multimedia bitstream MBS. Thevideo zone formatter 1300 rearranges the title editing units (VOB) St35in one video zone VZ in the scenario sequence defined by the user basedon the title sequence control signal St39 to generate the editedmultimedia stream data St43.

[0130] The multimedia bitstream MBS St43 edited according to theuser-defined scenario is then sent to the recorder 1200. The recorder1200 processes the edited multimedia stream data St43 to the data streamSt45 format of the recording medium M, and thus records the formatteddata stream St45 to the recording medium M. Note that the multimediabitstream MBS recorded to the recording medium M contains the volumefile structure VFS, which includes the physical address of the data onthe recording medium generated by the video zone formatter 1300.

[0131] Note that the encoded multimedia bitstream MBS St35 may be outputdirectly to the decoder to immediately reproduce the edited titlecontent. It will be obvious that the output multimedia bitstream MBSwill not in this case contain the volume file structure VFS.

[0132] Authoring decoder

[0133] A preferred embodiment of the authoring decoder DC used to decodethe multimedia bitstream MBS edited by the authoring encoder EC of thepresent invention, and thereby reproduce the content of each title unitaccording to the user-defined scenario, is described next below withreference to FIG. 3. Note that in the preferred embodiment describedbelow the multimedia bitstream St45 encoded by the authoring encoder ECis recorded to the recording medium M.

[0134] As shown in FIG. 3, the authoring decoder DC comprises amultimedia bitstream producer 2000, scenario selector 2100, decodingsystem controller 2300, stream buffer 2400, system decoder 2500, videobuffer 2600, sub-picture buffer 2700, audio buffer 2800, synchronizer2900, video decoder 3800, sub-picture decoder 3100, audio decoder 3200,synthesizer 3500, video data output terminal 3600, and audio data outputterminal 3700.

[0135] The bitstream producer 2000 comprises a recording media driveunit 2004 for driving the recording medium M; a reading head 2006 forreading the information recorded to the recording medium M and producingthe binary read signal St57; a signal processor 2008 for variouslyprocessing the read signal St57 to generate the reproduced bitstreamSt61; and a reproduction controller 2002.

[0136] The reproduction controller 2002 is connected to the decodingsystem controller 2300 from which the multimedia bitstream reproductioncontrol signal St53 is supplied, and in turn generates the reproductioncontrol signals St55 and St59 respectively controlling the recordingmedia drive unit (motor) 2004 and signal processor 2008.

[0137] So that the user-defined video, sub-picture, and audio portionsof the multimedia title edited by the authoring encoder EC arereproduced, the authoring decoder DC comprises a scenario selector 2100for selecting and reproducing the corresponding scenes (titles). Thescenario selector 2100 then outputs the selected titles as scenario datato the authoring decoder DC.

[0138] The scenario selector 2100 preferably comprises a keyboard, CPU,and monitor. Using the keyboard, the user then inputs the desiredscenario based on the content of the scenario input by the authoringencoder EC. Based on the keyboard input, the CPU generates the scenarioselection data St51 specifying the selected scenario. The scenarioselector 2100 is connected by an infrared communications device, forexample, to the decoding system controller 2300, to which it inputs thescenario selection data St51.

[0139] Based on the scenario selection data St51, the decoding systemcontroller 2300 then generates the bitstream reproduction control signalSt53 controlling the operation of the bitstream producer 2000.

[0140] The stream buffer 2400 has a specific buffer capacity used totemporarily store the reproduced bitstream St61 input from the bitstreamproducer 2000, extract the address information and initialsynchronization data SCR (system clock reference) for each stream, andgenerate bitstream control data St63. The stream buffer 2400 is alsoconnected to the decoding system controller 2300, to which it suppliesthe generated bitstream control data St63.

[0141] The synchronizer 2900 is connected to the decoding systemcontroller 2300 from which it receives the system clock reference SCRcontained in the synchronization control data St81 to set the internalsystem clock STC and supply the reset system clock St79 to the decodingsystem controller 2300.

[0142] Based on this system clock St79, the decoding system controller2300 also generates the stream read signal St65 at a specific intervaland outputs the read signal St65 to the stream buffer 2400.

[0143] Based on the supplied read signal St65, the stream buffer 2400outputs the reproduced bitstream St61 at a specific interval to thesystem decoder 2500 as bitstream St67.

[0144] Based on the scenario selection data St51, the decoding systemcontroller 2300 generates the decoding signal St69 defining the streamIds for the video, sub-picture, and audio bitstreams corresponding tothe selected scenario, and outputs to the system decoder 2500.

[0145] Based on the instructions contained in the decoding signal St69,the system decoder 2500 respectively outputs the video, sub-picture, andaudio bitstreams input from the stream buffer 2400 to the video buffer2600, sub-picture buffer 2700, and audio buffer 2800 as the encodedvideo stream St71, encoded sub-picture stream St73, and encoded audiostream St75.

[0146] The system decoder 2500 detects the presentation time stamp PTSand decoding time stamp DTS of the smallest control unit in eachbitstream St67 to generate the time information signal St77. This timeinformation signal St77 is supplied to the synchronizer 2900 through thedecoding system controller 2300 as the synchronization control dataSt81.

[0147] Based on this synchronization control data St81, the synchronizer2900 determines the decoding start timing whereby each of the bitstreamswill be arranged in the correct sequence after decoding, and thengenerates and inputs the video stream decoding start signal St89 to thevideo decoder 3800 based on this decoding timing. The synchronizer 2900also generates and supplies the sub-picture decoding start signal St91and audio stream decoding start signal St93 to the sub-picture decoder3100 and audio decoder 3200, respectively.

[0148] The video decoder 3800 generates the video output request signalSt84 based on the video stream decoding start signal St89, and outputsto the video buffer 2600. In response to the video output request signalSt84, the video buffer 2600 outputs the video stream St83 to the videodecoder 3800. The video decoder 3800 thus detects the presentation timeinformation contained in the video stream St83, and disables the videooutput request signal St84 when the length of the received video streamSt83 is equivalent to the specified presentation time. A video streamequal in length to the specified presentation time is thus decoded bythe video decoder 3800, which outputs the reproduced video signal St104to the synthesizer 3500.

[0149] The sub-picture decoder 3100 similarly generates the sub-pictureoutput request signal St86 based on the sub-picture decoding startsignal St91, and outputs to the sub-picture buffer 2700. In response tothe sub-picture output request signal St86, the sub-picture buffer 2700outputs the sub-picture stream St85 to the sub-picture decoder 3100.Based on the presentation time information contained in the sub-picturestream St85, the sub-picture decoder 3100 decodes a length of thesub-picture stream St85 corresponding to the specified presentation timeto reproduce and supply to the synthesizer 3500 the sub-picture signalSt99.

[0150] The synthesizer 3500 superimposes the video signal St104 andsub-picture signal St99 to generate and output the multi-picture videosignal St105 to the video data output terminal 3600.

[0151] The audio decoder 3200 generates and supplies to the audio buffer2800 the audio output request signal St88 based on the audio streamdecoding start signal St93. The audio buffer 2800 thus outputs the audiostream St87 to the audio decoder 3200. The audio decoder 3200 decodes alength of the audio stream St87 corresponding to the specifiedpresentation time based on the presentation time information containedin the audio stream St87, and outputs the decoded audio stream St101 tothe audio data output terminal 3700.

[0152] It is thus possible to reproduce a user-defined multimediabitstream MBS in real-time according to a user-defined scenario. Morespecifically, each time the user selects a different scenario theauthoring decoder DC is able to reproduce the title content desired bythe user in the desired sequence by reproducing the multimedia bitstreamMBS corresponding to the selected scenario.

[0153] It is therefore possible by means of the authoring system of thepresent invention to generate a multimedia bitstream according to pluraluser-defined scenarios by real-time or batch encoding multimedia sourcedata in a manner whereby the substreams of the smallest editing units(scenes), which can be divided into plural substreams, expressing thebasic title content are arranged in a specific time-base relationship.

[0154] The multimedia bitstream thus encoded can then be reproducedaccording to the one scenario selected from among plural possiblescenarios. It is also possible to change scenarios while playback is inprogress, i.e., to select a different scenario and dynamically generatea new multimedia bitstream according to the most recently selectedscenario. It is also possible to dynamically select and reproduce any ofplural scenes while reproducing the title content according to a desiredscenario.

[0155] It is therefore possible by means of the authoring system of thepresent invention to encode and not only reproduce but to repeatedlyreproduce a multimedia bitstream MBS in real-time.

[0156] A detail of the authoring system is disclosed Japanese PatentApplication filed Sep. 27, 1996, and entitled and assigned to the sameassignee as the present application.

[0157] Digital video disk (DVD)

[0158] An example of a digital video disk (DVD) with only one recordingsurface (a single-sided DVD) is shown in FIG. 4.

[0159] The DVD recording medium RC1 in the preferred embodiment of theinvention comprises a data recording surface RS1 to and from which datais written and read by emitting laser beam LS, and a protective layerPL1 covering the data recording surface RS1. A backing layer BL1 is alsoprovided on the back of data recording surface RS1. The side of the diskon which protective layer PL1 is provided is therefore referred to belowas side SA (commonly “side A”), and the opposite side (on which thebacking layer BL1 is provided) is referred to as side SB (“side B”).Note that digital video disk recording media having a single datarecording surface RS1 on only one side such as this DVD recording mediumRC1 is commonly called a single-sided single layer disk.

[0160] A detailed illustration of area C1 in FIG. 4 is shown in FIG. 5.Note that the data recording surface RS1 is formed by applying ametallic thin film or other reflective coating as a data layer 4109 on afirst transparent layer 4108 having a particular thickness Tl. Thisfirst transparent layer 4108 also functions as the protective layer PL1.A second transparent substrate 4111 of a thickness T2 functions as thebacking layer BL1, and is bonded to the first transparent layer 4108 bymeans of an adhesive layer 4110 disposed therebetween.

[0161] A printing layer 4112 for printing a disk label may also bedisposed on the second transparent substrate 4111 as necessary. Theprinting layer 4112 does not usually cover the entire surface area ofthe second transparent substrate 4111 (backing layer BL1), but only thearea needed to print the text and graphics of the disk label. The areaof second transparent substrate 4111 to which the printing layer 4112 isnot formed may be left exposed. Light reflected from the data layer 4109(metallic thin film) forming the data recording surface RS1 cantherefore be directly observed where the label is not printed when thedigital video disk is viewed from side SB. As a result, the backgroundlooks like a silver-white over which the printed text and graphics floatwhen the metallic thin film is an aluminum thin film, for example.

[0162] Note that it is only necessary to provide the printing layer 4112where needed for printing, and it is not necessary to provide theprinting layer 4112 over the entire surface of the backing layer BL1.

[0163] A detailed illustration of area C2 in FIG. 5 is shown in FIG. 6.Pits and lands are molded to the common contact surface between thefirst transparent layer 4108 and the data layer 4109 on side SA fromwhich data is read by emitting a laser beam LS, and data is recorded byvarying the lengths of the pits and lands (i.e., the length of theintervals between the pits). More specifically, the pit and landconfiguration formed on the first transparent layer 4108 is transferredto the data layer 4109. The lengths of the pits and lands is shorter,and the pitch of the data tracks formed by the pit sequences isnarrower, than with a conventional Compact Disc (CD). The surfacerecording density is therefore greatly improved.

[0164] Side SA of the first transparent layer 4108 on which data pitsare not formed is a flat surface. The second transparent substrate 4111is for reinforcement, and is a transparent panel made from the samematerial as the first transparent layer 4108 with both sides flat.Thicknesses T1 and T2 are preferably equal and commonly approximately0.6 mm, but the invention shall not be so limited.

[0165] As with a CD, information is read by irradiating the surface witha laser beam LS and detecting the change in the reflectivity of thelight spot. Because the objective lens aperture NA can be large and thewavelength l of the light beam small in a digital video disk system, thediameter of the light spot Ls used can be reduced to approximately{fraction (1/1.6)} the light spot needed to read a CD. Note that thismeans the resolution of the laser beam LS in the DVD system isapproximately 1.6 times the resolution of a conventional CD system.

[0166] The optical system used to read data from the digital video diskuses a short 650 nm wavelength red semiconductor laser and an objectivelens with a 0.6 mm aperture NA. By thus also reducing the thickness T ofthe transparent panels to 0.6 mm, more than 5 GB of data can be storedto one side of a 120 mm diameter optical disk.

[0167] It is therefore possible to store motion picture (video) imageshaving an extremely large per unit data size to a digital video disksystem disk without losing image quality because the storage capacity ofa single-sided, single-layer recording medium RC1 with one datarecording surface RS1 as thus described is nearly ten times the storagecapacity of a conventional CD. As a result, while the video presentationtime of a conventional CD system is approximately 74 minutes if imagequality is sacrificed, high quality video images with a videopresentation time exceeding two hours can be recorded to a DVD.

[0168] The digital video disk is therefore well-suited as a recordingmedium for video images.

[0169] A digital video disk recording medium with plural recordingsurfaces RS as described above is shown in FIGS. 7 and 8. The DVDrecording medium RC2 shown in FIG. 7 comprises two recording surfaces,i.e., first recording surface RS1 and semi-transparent second recordingsurface RS2, on the same side, i.e. side SA, of the disk. Data can besimultaneously recorded or reproduced from these two recording surfacesby using different laser beams LS1 and LS2 for the first recordingsurface RS1 and the second recording surface RS2. It is also possible toread/write both recording surfaces RS1 and RS2 using only one of thelaser beams LS1 or LS2. Note that recording media thus comprised arecalled “single-side, dual-layer disks.”

[0170] It should also be noted that while two recording surfaces RS1 andRS2 are provided in this example, it is also possible to produce digitalvideo disk recording media having more than two recording surfaces RS.Disks thus comprised are known as “single-sided, multi-layer disks.”

[0171] Though comprising two recording surfaces similarly to therecording media shown in FIG. 7, the DVD recording medium RC3 shown inFIG. 8 has the recording surfaces on opposite sides of the disk, i. e.,has the first data recording surface RS1 on side SA and the second datarecording surface RS2 on side SB. It will also be obvious that whileonly two recording surfaces are shown on one digital video disk in thisexample, more than two recording surfaces may also be formed on adouble-sided digital video disk. As with the recording medium shown inFIG. 7, it is also possible to provide two separate laser beams LS1 andLS2 for recording surfaces RS1 and RS2, or to read/write both recordingsurfaces RS1 and RS2 using a single laser beam. Note that this type ofdigital video disk is called a “double-sided, dual-layer disk.” It willalso be obvious that a double-sided digital video disk can be comprisedwith two or more recording surfaces per side. This type of disk iscalled a “double-sided, multi-layer disk.”

[0172] A plan view from the laser beam LS irradiation side of therecording surface RS of the DVD recording medium RC is shown in FIG. 9and FIG. 10. Note that a continuous spiral data recording track TR isprovided from the inside circumference to the outside circumference ofthe DVD. The data recording track TR is divided into plural sectors eachhaving the same known storage capacity. Note that for simplicity onlythe data recording track TR is shown in FIG. 9 with more than threesectors per revolution.

[0173] As shown in FIG. 9, the data recording track TR is normallyformed clockwise inside to outside (see arrow DrA) from the inside endpoint IA at the inside circumference of disk RCA to the outside endpoint OA at the outside circumference of the disk with the disk RCArotating counterclockwise RdA. This type of disk RCA is called aclockwise disk, and the recording track formed thereon is called aclockwise track TRA.

[0174] Depending upon the application, the recording track TRB may beformed clockwise from outside to inside circumference (see arrow DrB inFIG. 10) from the outside end point OB at the outside circumference ofdisk RCB to the inside end point IB at the inside circumference of thedisk with the disk RCB rotating clockwise RdB. Because the recordingtrack appears to wind counterclockwise when viewed from the insidecircumference to the outside circumference on disks with the recordingtrack formed in the direction of arrow DrB, these disks are referred toas counterclockwise disk RCB with counterclockwise track TRB todistinguish them from disk RCA in FIG. 9. Note that track directions DrAand DrB are the track paths along which the laser beam travels whenscanning the tracks for recording and playback. Direction of diskrotation RdA in which disk RCA turns is thus opposite the direction oftrack path DrA, and direction of disk rotation RdB in which disk RCBturns is thus opposite the direction of track path DrB.

[0175] An exploded view of the single-sided, dual-layer disk RC2 shownin FIG. 7 is shown as disk RC2 o in FIG. 11. Note that the recordingtracks formed on the two recording surfaces run in opposite directions.Specifically, a clockwise recording track TRA as shown in FIG. 9 isformed in clockwise direction DrA on the (lower) first data recordingsurface RS1, and a counterclockwise recording track TRB formed incounterclockwise direction DrB as shown in FIG. 10 is provided on the(upper) second data recording surface RS2. As a result, the outside endpoints OA and OB of the first and second (top and bottom) tracks are atthe same radial position relative to the center axis of the disk RC2 o.Note that track paths DrA and DrB of tracks TR are also the dataread/write directions to disk RC. The first and second (top and bottom)recording tracks thus wind opposite each other with this disk RC, i.e.,the track paths DrA and DrB of the top and bottom recording layers areopposite track paths.

[0176] Opposite track path type, single-sided, dual-layer disks RC2 orotate in direction RdA corresponding to the first recording surface RS1with the laser beam LS travelling along track path DrA to trace therecording track on the first recording surface RS1. When the laser beamLS reaches the outside end point OA, the laser beam LS can be refocusedto end point OB on the second recording surface RS2 to continue tracingthe recording track from the first to the second recording surfaceuninterrupted. The physical distance between the recording tracks TRAand TRB on the first and second recording surfaces RS1 and RS2 can thusbe instantaneously eliminated by simply adjusting the focus of the laserbeam LS.

[0177] It is therefore possible with an opposite track path type,single-sided, dual-layer disk RC2 o to easily process the recordingtracks disposed to physically discrete top and bottom recording surfacesas a single continuous recording track. It is therefore also possible inan authoring system as described above with reference to FIG. 1 tocontinuously record the multimedia bitstream MBS that is the largestmultimedia data management unit to two discrete recording surfaces RS1and RS2 on a single recording medium RC2 o.

[0178] It should be noted that the tracks on recording surfaces RS1 andRS2 can be wound in the directions opposite those described above, i.e.,the counterclockwise track TRB may be provided on the first recordingsurface RS1 and the clockwise track TRA on the second recording surfaceRS2. In this case the direction of disk rotation is also changed to aclockwise rotation RdB, thereby enabling the two recording surfaces tobe used as comprising a single continuous recording track as describedabove. For simplification, a further example of this type of disk istherefore neither shown nor described below.

[0179] It is therefore possible by thus constructing the digital videodisk to record the multimedia bitstream MBS for a feature-length titleto a single opposite track path type, single-sided, dual-layer disk RC2o. Note that this type of digital video disk medium is called asingle-sided dual-layer disk with opposite track paths.

[0180] Another example of the single-sided, dual-layer DVD recordingmedium RC2 shown in FIG. 7 is shown as disk RC2 p in FIG. 12. Therecording tracks formed on both first and second recording surfaces RS1and RS2 are clockwise tracks TRA as shown in FIG. 9. In this case, thesingle-sided, dual-layer disk RC2 p rotates counterclockwise in thedirection of arrow RdA, and the direction of laser beam LS travel is thesame as the direction of the track spiral, i.e., the track paths of thetop and bottom recording surfaces are mutually parallel (parallel trackpaths). The outside end points OA of both top and bottom tracks areagain preferably positioned at the same radial position relative to thecenter axis of the disk RC2 p as described above. As also describedabove with disk RC2 o shown in FIG. 11, the access point can beinstantaneously shifted from outside end point OA of track TRA on thefirst recording surface RS1 to the outside end point OA of track TRA onthe second recording surface RS2 by appropriately adjusting the focus ofthe laser beam LS at outside end point OA.

[0181] However, for the laser beam LS to continuously access theclockwise recording track TRA on the second recording surface RS2, therecording medium RC2 p must be driven in the opposite direction(clockwise, opposite direction RdA). Depending-on the radial position ofthe laser beam LS, however, it is inefficient to change the rotationaldirection of the recording medium. As shown by the diagonal arrow inFIG. 12, the laser beam LS is therefore moved from the outside end pointOA of the track on the first recording surface RS1 to the inside endpoint IA of the track on the second recording surface RS2 to use thesephysically discrete recording tracks. as one logically continuousrecording track.

[0182] Rather than using the recording tracks on top and bottomrecording surfaces as one continuous recording track, it is alsopossible to use the recording tracks to record the multimedia bitstreamsMBS for different titles. This type of digital video disk recordingmedium is called a “single-sided, dual-layer disk with parallel trackpaths.”

[0183] Note that if the direction of the tracks formed on the recordingsurfaces RS1 and RS2 is opposite that described above, i.e.,counterclockwise recording tracks TRB are formed, disk operation remainsthe same as that described above except for the direction of diskrotation, which is clockwise as shown by arrow RdB.

[0184] Whether using clockwise or counterclockwise recording tracks, thesingle-sided, dual-layer disk RC2 p with parallel track paths thusdescribed is well-suited to storing on a single disk encyclopedia andsimilar multimedia bitstreams comprising multiple titles that arefrequently and randomly accessed.

[0185] An exploded view of the dual-sided single-layer DVD recordingmedium RC3 comprising one recording surface layer RS1 and RS2 on eachside as shown in FIG. 8 is shown as DVD recording medium RC3 s in FIG.13. Clockwise recording track TRA is provided on the one recordingsurface RS1, and a counterclockwise recording track TRB is provided onthe other recording surface RS2. As in the preceding recording media,the outside end points OA and OB of the recording tracks on eachrecording surface are preferably positioned at the same radial positionrelative to the center axis of the DVD recording medium RC3 s.

[0186] Note that while the recording tracks on these recording surfacesRS1 and RS2 rotate in opposite directions, the track paths aresymmetrical. This type of recording medium is therefore known as adouble-sided dual layer disk with symmetrical track paths. Thisdouble-sided dual layer disk with symmetrical track paths RC3 s rotatesin direction RdA when reading/writing the first recording surface RS1.As a result, the track path on the second recording surface RS2 on theopposite side is opposite the direction DrB in which the track winds,i.e., direction DrA. Accessing both recording surfaces RS1 and RS2 usinga single laser beam LS is therefore not realistic irrespective ofwhether access is continuous or non-continuous. In addition, amultimedia bitstream MBS is separately recorded to the recordingsurfaces on the first and second sides of the disk.

[0187] A different example of the double-sided single layer disk RC3shown in FIG. 8 is shown in FIG. 14 as disk RC3 a. Note that this diskcomprises clockwise recording tracks TRA as shown in FIG. 9 on bothrecording surfaces RS1 and RS2. As with the preceding recording media,the outside end points OA and OA of the recording tracks on eachrecording surface are preferably positioned at the same radial positionrelative to the center axis of the DVD recording medium RC3 a. Unlikethe double-sided dual layer disk with symmetrical track paths RC3 sdescribed above, the tracks on these recording surfaces RS1 and RS2 areasymmetrical. This type of disk is therefore known as a double-sideddual layer disk with asymmetrical track paths. This double-sided duallayer disk with asymmetrical track paths RC3 a rotates in direction RdAwhen reading/writing the first recording surface RS1. As a result, thetrack path on the second recording surface RS2 on the opposite side isopposite the direction DrA in which the track winds, i.e., directionDrB.

[0188] This means that if a laser beam LS is driven continuously fromthe inside circumference to the outside circumference on the firstrecording surface RS1, and then from the outside circumference to theinside circumference on the second recording surface RS2, both sides ofthe recording medium RC3 a can be read/written without turning the diskover and without providing different laser beams for the two sides.

[0189] The track paths for recording surfaces RS1 and RS2 are also thesame with this double-sided dual layer disk with asymmetrical trackpaths RC3 a. As a result, it is also possible to read/write both sidesof the disk without providing separate laser beams for each side if therecording medium RC3 a is turned over between sides, and the read/writeapparatus can therefore be constructed economically.

[0190] It should be noted that this recording medium remainsfunctionally identical even if counterclockwise recording track TRB isprovided in place of clockwise recording track TRA on both recordingsurfaces RS1 and RS2.

[0191] As described above, the true value of a DVD system whereby thestorage capacity of the recording medium can be easily increased byusing a multiple layer recording surface is realized in multimediaapplications whereby plural video data units, plural audio data units,and plural graphics data units recorded to a single disk are reproducedthrough interactive operation by the user.

[0192] It is therefore possible to achieve one longstanding desire ofsoftware (programming) providers, specifically, to provide programmingcontent such as a commercial movie on a single recording medium inplural versions for different language and demographic groups whileretaining the image quality of the original.

[0193] Parental Control

[0194] Content providers of movie and video titles have conventionallyhad to produce, supply, and manage the inventory of individual titles inmultiple languages, typically the language of each distribution market,and multi-rated title packages conforming to the parental control(censorship) regulations of individual countries in Europe and NorthAmerica. The time and resources required for this are significant. Whilehigh image quality is obviously important, the programming content mustalso be consistently reproducible.

[0195] The digital video disk recording medium is close to solving theseproblems.

[0196] Multiple Angles

[0197] One interactive operation widely sought in multimediaapplications today is for the user to be able to change the positionfrom which a scene is viewed during reproduction of that scene. Thiscapability is achieved by means of the multiple angle function.

[0198] This multiple angle function makes possible applications whereby,for example, a user can watch a baseball game from different angles (orvirtual positions in the stadium), and can freely switch between theviews while viewing is in progress. In this example of a baseball game,the available angles may include a position behind the backstop centeredon the catcher, batter, and pitcher; one from behind the backstopcentered on a fielder, the pitcher, and the catcher; and one from centerfield showing the view to the pitcher and catcher.

[0199] To meet these requirements, the digital video disk system usesMPEG, the same basic standard format used with Video-Cds to record thevideo, audio, graphics, and other signal data. Because of thedifferences in storage capacity, transfer rates, and signal processingperformance within the reproduction apparatus, DVD uses MPEG2, thecompression method and data format of which differ slightly from theMPEG1 format used with Video-Cds.

[0200] It should be noted that the content of and differences betweenthe MPEG1 and MPEG2 standards have no direct relationship to the intentof the present invention, and further description is therefore omittedbelow (for more information, see MPEG specifications ISO-11172 andISO-13818).

[0201] The data structure of the DVD system according to the presentinvention is described in detail below with reference to FIGS. 16, 17,18, 19, 20, and 21.

[0202] Multi-scene Control

[0203] A fully functional and practical parental lock playback functionand multi-angle scene playback function must enable the user to modifythe system output in minor, subtle ways while still presentingsubstantially the same video and audio output. If these functions areachieved by preparing and recording separate titles satisfying each ofthe many possible parental lock and multi-angle scene playback requests,titles that are substantially identical and differ in only minor waysmust be recorded to the recording medium. This results in identical databeing repeatedly recorded to the larger part of the recording medium,and significantly reduces the utilization efficiency of the availablestorage capacity. More particularly, it is virtually impossible torecord discrete titles satisfying every possible request even using themassive capacity of the digital video disk medium. While it may beconcluded that this problem can be easily solved by increasing thecapacity of the recording medium, this is an obviously undesirablesolution when the effective use of available system resources-isconsidered.

[0204] Using multi-scene control, the concept of which is described inanother section below, in a DVD system, it is possible to dynamicallyconstruct titles for numerous variations of the same basic content usingthe smallest possible amount of data, and thereby effectively utilizethe available system resources (recording medium). More specifically,titles that can be played back with numerous variations are constructedfrom basic (common) scene periods containing data common to each title,and multi-scene periods comprising groups of different scenescorresponding to the various requests. During reproduction, the user isable to freely and at any time select particular scenes from themulti-scene periods to dynamically construct a title conforming to thedesired content, e.g., a title omitting certain scenes using theparental lock control function.

[0205] Note that multi-scene control enabling a parental lock playbackcontrol function and multi-angle scene playback is described in anothersection below with reference to FIG. 21.

[0206] Data Structure of the DVD System

[0207] The data structure used in the authoring system of a digitalvideo disk system according to the present invention is shown in FIG.22. To record a multimedia bitstream MBS, this digital video disk systemdivides the recording medium into three major recording areas, thelead-in area LI, the volume space VS, and the lead-out area LO.

[0208] The lead-in area-LI is provided at the inside circumference areaof the optical disk. In the disks described with reference to FIGS. 9and 10, the lead-in area LI is positioned at the inside end points IAand IB of each track. Data for stabilizing the operation of thereproducing apparatus when reading starts is written to the lead-in areaLI.

[0209] The lead-out area LO is correspondingly located at the outsidecircumference of the optical disk, i.e., at outside end points OA and OBof each track in the disks described with reference to FIGS. 9 and 10.Data identifying the end of the volume space VS is recorded in thislead-out area LO.

[0210] The volume space VS is located between the lead-in area LI andlead-out area LO, and is recorded as a one-dimensional array of n+1(where n is an integer greater than or equal to zero) 2048-byte logicsectors LS. The logic sectors LS are sequentially number #0, #1, #2, . .. #n. The volume space VS is also divided into a volume and filestructure management area VFS and a file data structure area FDS.

[0211] The volume and file structure management area VFS comprises m+1logic sectors LS#0 to LS#m (where m is an integer greater than or equalto zero and less than n. The file data structure FDS comprises n-m logicsectors LS #m+1 to LS #n.

[0212] Note that this file data structure area FDS corresponds to themultimedia bitstream MBS shown in FIG. 1 and described above.

[0213] The volume file structure VFS is the file system for managing thedata stored to the volume space VS as files, and is divided into logicsectors LS#0-LS#m where m is the number of sectors required to store alldata needed to manage the entire disk, and is a natural number less thann. Information for the files stored to the file data structure area FDSis written to the volume file structure VFS according to a knownspecification such as ISO-9660 or ISO-13346.

[0214] The file data structure area FDS comprises n-m logic sectorsLS#m-LS#n, each comprising a video manager VMG sized to an integermultiple of the logic sector (2048×I, where I is a known integer), and kvideo title sets VTS #1-VTS#k (where k is a natural number less than100).

[0215] The video manager VMG stores the title management information forthe entire disk, and information for building a volume menu used to setand change reproduction control of the entire volume.

[0216] Any video title set VTS #k is also called a “video file”representing a title comprising video, audio, and/or still image data.

[0217] The internal structure of each video title set VTS shown in FIG.22 is shown in FIG. 16. Each video title set VTS comprises VTSinformation VTSI describing the management information for the entiredisk, and the VTS title video objects VOB (VTSTT_VOBS), i.e., the systemstream of the multimedia bitstream. The VTS information VTSI isdescribed first below, followed by the VTS title VOBS.

[0218] The VTS information primarily includes the VTSI management tableVTSI_MAT and VTSPGC information table VTS_PGCIT.

[0219] The VTSI management table VTSI_MAT stores such information as theinternal structure of the video title set VTS, the number of selectableaudio streams contained in the video title set VTS, the number ofsub-pictures, and the video title set VTS location (storage address).

[0220] The VTSPGC information table VTS_PGCIT records i (where i is anatural number) program chain (PGC) data blocks VTS_PGCI #1-VTS_PGCI #ifor controlling the playback sequence. Each of the table entriesVTS_PGCI #i is a data entry expressing the program chain, and comprisesj (where j is a natural number) cell playback information blocks C_PBI#1-C_PBI #j. Each cell playback information block C_PBI #j contains theplayback sequence of the cell and playback control information.

[0221] The program chain PGC is a conceptual structure describing thestory of the title content, and therefore defines the structure of eachtitle by describing the cell playback sequence. Note that these cellsare described in detail below.

[0222] If, for example, the video title set information relates to themenus, the video title set information VTSI is stored to a buffer in theplayback device when playback starts. If the user then presses a MENUbutton on a remote control device, for example, during playback, theplayback device references the buffer to fetch the menu information anddisplay the top menu #1. If the menus are hierarchical, the main menustored as program chain information VTS_PGCI #1 may be displayed, forexample, by pressing the MENU button, VTS_PGCI #2-#9 may correspond tosubmenus accessed using the numeric keypad on the remote control, andVTS_PGCI #10 and higher may correspond to additional submenus furtherdown the hierarchy. Alternatively, VTS_PGCI #1 may be the top menudisplayed by pressing the MENU button, while VTS_PGCI #2 and higher maybe voice guidance reproduced by pressing the corresponding numeric key.

[0223] The menus themselves are expressed by the plural program chainsdefined in this table. As a result, the menus may be freely constructedin various ways, and shall not be limited to hierarchical ornon-hierarchical menus or menus containing voice guidance.

[0224] In the case of a movie, for example, the video title setinformation VTSI is stored to a buffer in the playback device whenplayback starts, the playback device references the cell playbacksequence described by the program chain PGC, and reproduces the systemstream.

[0225] The “cells” referenced here may be all or part of the systemstream, and are used as access points during playback. Cells cantherefore be used, for example, as the “chapters” into which a title maybe divided.

[0226] Note that each of the PGC information entries C_PBI #j containboth cell playback processing information and a cell information table.The cell playback processing information comprises the processinginformation needed to reproduce the cell, such as the presentation timeand number of repetitions. More specifically, this information includesthe cell block mode CBM, cell block type CBT, seamless playback flagSPF, interleaved allocation flag IAF, STC resetting flag STCDF, cellpresentation time C_PBTM, seamless angle change flag SACF, first cellVOBU start address C_FVOBU_SA, and the last cell VOBU start addressC_LVOBU_SA.

[0227] Note that seamless playback refers to the reproduction in adigital video disk system of multimedia data including video, audio, andsub-picture data without intermittent breaks in the data or information.Seamless playback is described in detail in another section below withreference to FIG. 23 and FIG. 24.

[0228] The cell block mode CBM indicates whether plural cells constituteone functional block. The cell playback information of each cell in afunctional block is arranged consecutively in the PGC information. Thecell block mode CBM of the first cell playback information in thissequence contains the value of the first cell in the block, and the cellblock mode CBM of the last cell playback information in this sequencecontains the value of the last cell in the block. The cell block modeCBM of each cell arrayed between these first and last cells contains avalue indicating that the cell is a cell between these first and lastcells in that block.

[0229] The cell block type CBT identifies the type of the blockindicated by the cell block mode CBM. For example, when a multiple anglefunction is enabled, the cell information corresponding to each of thereproducible angles is programmed as one of the functional blocksmentioned above, and the type of these functional blocks is defined by avalue identifying “angle” in the cell block type CBT for each cell inthat block.

[0230] The seamless playback flag SPF simply indicates whether thecorresponding cell is to be linked and played back seamlessly with thecell or cell block reproduced immediately therebefore. To seamlesslyreproduce a given cell with the preceding cell or cell block, theseamless playback flag SPF is set to 1 in the cell playback informationfor that cell; otherwise SPF is set to 0.

[0231] The interleaved allocation flag IAF stores a value identifyingwhether the cell exists in a contiguous or interleaved block. If thecell is part of an interleaved block, the flag IAF is set to 1;otherwise it is set to 0.

[0232] The STC resetting flag STCDF identifies whether the system timeclock STC used for synchronization must be reset when the cell is playedback; when resetting the system time clock STC is necessary, the STCresetting flag STCDF is set to 1.

[0233] The seamless angle change flag SACF stores a value indicatingwhether a cell in a multi-angle period should be connected seamlessly atan angle change. If the angle change is seamless, the seamless anglechange flag SACF is set to 1; otherwise it is set to 0.

[0234] The cell presentation time C PBTM expresses the cell presentationtime with—video frame precision.

[0235] The first cell VOBU start address C_FVOBU_SA is the VOBU startaddress of the first cell in a block, and is also expressed as thedistance from the logic sector of the first cell in the VTS title VOBS(VTSTT_VOBS) as measured by the number of sectors.

[0236] The last cell VOBU start address C_LVOBU_SA is the VOBU startaddress of the last cell in the block. The value of this address isexpressed as the distance from the logic sector of the first cell in theVTS title VOBS (VTSTT_VOBS) as measured by the number of sectors.

[0237] The VTS title VOBS (VTSTT_VOBS), i.e., the multimedia systemstream data, is described next. The system stream data VTSTT_VOBScomprises i (where i is a natural number) system streams SS, each ofwhich is referred to as a “video object” (VOB). Each video object VOB#1-VOB #i comprises at least one video data block interleaved with up toa maximum eight audio data blocks and up to a maximum 32 sub-picturedata blocks.

[0238] Each video object VOB comprises q (where q is a natural number)cells C#1-C#q. Each cell C comprises r (where r is a natural number)video object units VOBU #1-VOBU #r.

[0239] Each video object unit VOBU comprises plural groups_of_picturesGOP, and the audio and sub-pictures corresponding to the playback ofsaid plural groups_of_pictures GOP. Note that the group_of_pictures GOPcorresponds to the video encoding refresh cycle. Each video object unitVOBU also starts with an NV pack, i.e., the control data for that VOBU.

[0240] The structure of the navigation packs NV is described withreference to FIG. 19.

[0241] Before describing the navigation pack NV, the internal structureof the video zone VZ (see FIG. 22), i.e., the system stream St35 encodedby the authoring encoder EC described with reference to FIG. 25, isdescribed with reference to FIG. 17.Note that the encoded video streamSt15 shown in FIG. 17 is the compressed one-dimensional video datastream encoded by the video encoder 300. The encoded audio stream St19is likewise the compressed one-dimensional audio data streammultiplexing the right and left stereo audio channels encoded by theaudio encoder 700. Note that the audio signal shall not be limited to astereo signal, and may also be a multichannel surround-sound signal.

[0242] The system stream (title editing unit VOB) St35 is a onedimensional array of packs with a byte size corresponding to the logicsectors LS #n having a 2048-byte capacity as described using FIG. 22. Astream control pack is placed at the beginning of the title editing unit(VOB) St35, i.e., at the beginning of the video object unit VOBU. Thisstream control pack is called the “navigation pack NV”, and records thedata arrangement in the system stream and other control information.

[0243] The encoded video stream St and the encoded audio stream St19 arepacketized in byte units corresponding to the system stream packs. Thesepackets are shown in FIG. 17 as packets V1, V2, V3, V4 . . . and A1, A2,A3 . . . . As shown in FIG. 17, these packets are interleaved in theappropriate sequence as system stream St35, thus forming a packetstream, with consideration given to the decoder buffer size and the timerequired by the decoder to expand the video and audio data packets. Inthe example shown in FIG. 17, the packet stream is interleaved in thesequence V1, V2, A1, V3, V4, A2 . . . .

[0244] Note that the sequence shown in FIG. 17 interleaves one videodata unit with one audio data unit. Significantly increasedrecording/playback capacity, high speed recording/playback, andperformance improvements in the signal processing LSI enable the DVDsystem to record plural audio data and plural sub-picture data.(graphics data) to one video data unit in a single interleaved MPEGsystem stream, and thereby enable the user to select the specific audiodata and sub-picture data to be reproduced during playback. Thestructure of the system stream used in this type of DVD system is shownin FIG. 18 and described below.

[0245] As in FIG. 17, the packetized encoded video stream St15 is shownin FIG. 18 as V, V2, V3, V4, . . . . In this example, however, there isnot just one encoded audio stream St19, but three encoded audio streamsSt19A, St19B, and St19C input as the source data. There are also twoencoded sub-picture streams St17A and St17B input as the source datasub-picture streams. These six compressed data streams, St15, St19A,St19B, St19C, St17A and St17B, are interleaved to a single system streamSt35.

[0246] The video data is encoded according to the MPEG specificationwith the group_of_pictures GOP being the unit of compression. Ingeneral, each group_of_pictures GOP contains 15 frames in the case of anNTSC signal, but the specific number of frames compressed to one GOP isvariable. The stream management pack, which describes the managementdata containing, for example, the relationship between interleaved data,is also interleaved at the GOP unit interval. Because thegroup_of_pictures GOP unit is based on the video data, changing thenumber of video frames per GOP unit changes the interval of the streammanagement packs. This interval is expressed in terms of thepresentation time on the digital video disk within a range from 0.4 sec.to 1.0 sec. referenced to the GOP unit. If the presentation time ofcontiguous plural GOP units is less than 1 sec., the management datapacks for the video data of the plural GOP units is interleaved to asingle stream.

[0247] These management data packs are referred to as navigation packsNV in the digital video disk system. The data from one navigation packNV to the packet immediately preceding the next navigation pack NV formsone video object unit VOBU. In general, one contiguous playback unitthat can be defined as one scene is called a video object VOB, and eachvideo object VOB contains plural video object units VOBU. Data sets ofplural video objects VOB form a VOB set (VOBS). Note that these dataunits were first used in the digital video disk.

[0248] When plural of these data streams are interleaved, the navigationpacks NV defining the relationship between the interleaved packs mustalso be interleaved at a defined unit known as the pack number unit.Each group_of_pictures GOP is normally a unit containing approximately0.5 sec. of video data, which is equivalent to the presentation timerequired for 12-15 frames, and one navigation pack NV is generallyinterleaved with the number of data packets required for thispresentation time.

[0249] The stream management information contained in the interleavedvideo, audio, and sub-picture data packets constituting the systemstream is described below with reference to FIG. 19 As shown in FIG. 19,the data contained in the system stream is recorded in a format packedor packetized according to the MPEG2 standard. The packet structure isessentially the same for video, audio, and sub-picture data. One pack inthe digital video disk system has a 2048 byte capacity as describedabove, and contains a pack header PKH and one packet PES; each packetPES contains a packet header PTH and data block.

[0250] The pack header PKH records the time at which that pack is to besent from stream buffer 2400 to system decoder 2500 (see FIG. 26), i.e.,the system clock reference SCR defining the reference time forsynchronized audio-visual data playback. The MPEG standard assumes thatthe system clock reference SCR is the reference clock for the entiredecoder operation. With such disk media as the digital video disk,however, time management specific to individual disk players can beused, and a reference clock for the decoder system is. thereforeseparately provided.

[0251] The packet header-PTH similarly contains a presentation timestamp PTS and a decoding time stamp DTS, both of which are placed in thepacket before the access unit (the decoding unit). The presentation timestamp PTS defines the time at which the video data or audio datacontained in the packet should be output as the playback output afterbeing decoded, and the decoding time stamp DTS defines the time at whichthe video stream should be decoded. Note that the presentation timestamp PTS effectively defines the display start timing of the accessunit, and the decoding time stamp DTS effectively defines the decodingstart timing of the access unit. If the PTS and DTS are the same time,the DTS is omitted.

[0252] The packet header PTH also contains an 8-bit field called thestream ID identifying the packet type, i.e., whether the packet is avideo packet containing a video data stream, a private packet, or anMPEG audio packet.

[0253] Private packets under the MPEG2 standard are data packets ofwhich the content can be freely defined. Private packet 1 in thisembodiment of the invention is used to carry audio data other than theMPEG audio data, and sub-picture data; private packet 2 carries the PCIpacket and DSI packet.

[0254] Private packets 1 and 2 each comprise a packet header, privatedata area, and data area. The private data area contains an 8-bitsub-stream ID indicating whether the recorded data is audio data orsub-picture data. The audio data defined by private packet 2 may bedefined as any of eight types #0-#7 of linear PCM or AC-3 encoded data.Sub-picture data may be defined as one of up to 32 types #0-#31.

[0255] The data area is the field to which data compressed according tothe MPEG2 specification is written if the stored data is video data;linear PCM, AC-3, or MPEG encoded data is written if audio data isstored; or graphics data compressed by runlength coding is written ifsub-picture data is stored.

[0256] MPEG2-compressed video data may be compressed by constant bitrate (CBR) or variable bit rate (VBR) coding. With constant bit ratecoding, the video stream is input continuously to the video buffer at aconstant rate. This contrasts with variable bit rate coding in which thevideo stream is input intermittently to the video buffer, thereby makingit possible to suppress the generation of unnecessary code. Bothconstant bit rate and variable bit rate coding can be used in thedigital video disk system.

[0257] Because MPEG video data is compressed with variable lengthcoding, the data quantity in each group_of_pictures GOP is not constant.The video and audio decoding times also differ, and the time-baserelationship between the video and audio data read from an optical disk,and the time-base relationship between the video and audio data outputfrom the decoder, do not match. The method of time-base synchronizingthe video and audio data is therefore described in detail below withreference to FIG. 26, but is described briefly below based on constantbit rate coding.

[0258] The navigation pack NV structure is shown in FIG. 20. Eachnavigation pack NV starts with a pack header PKH, and contains a PCIpacket and DSI packet.

[0259] As described above, the pack header PKH records the time at whichthat pack is to be sent from stream buffer 2400 to system decoder 2500(see FIG. 26 ), i.e., the system clock reference SCR defining thereference time for synchronized audio-visual data playback.

[0260] Each PCI packet contains PCI General Information (PCI_GI) andAngle Information for Non-seamless playback (NMSL_AGLI).

[0261] The PCI General Information (PCI_GI) declares the display time ofthe first video frame (the Start PTM of VOBU (VOBU_S_PTM)), and thedisplay time of the last video frame (End PTM of VOBU (VOBU_E_PTM)), inthe corresponding video object unit VOBU with system clock precision (90Khz).

[0262] The Angle Information for Non-seamless playback (NMSL_AGLI)states the read start address of the corresponding video object unitVOBU when the angle is changed expressed as the number of sectors fromthe beginning of the video object VOB. Because there are nine or fewerangles in this example, there are nine angle address declaration cells:Destination Address of Angle Cell #1 for Non-seamless playback(NMSL_AGL_Cl_DSTA) to Destination Address of Angle Cell #9 forNon-seamless playback (NMSL_AGL_C9_DSTA).

[0263] Each DSI packet contains DSI General Information (DSI GI),Seamless Playback Information (SML_PBI), and Angle Information forSeamless playback (SML_AGLI).

[0264] The DSI General Information (DSI_GI) declares the address of thelast pack in the video object unit VOBU, i. e., the End Address for VOB(VOBU_EA), expressed as the number of sectors from the beginning of thevideo object unit VOBU.

[0265] While seamless playback is described in detail later, it shouldbe noted that the continuously read data units must be interleaved(multiplexed) at the system stream level as an interleaved unit ILVU inorder to seamlessly reproduce split or combined titles. Plural systemstreams interleaved with the interleaved unit ILVU as the smallest unitare defined as an interleaved block.

[0266] The Seamless Playback Information (SML_PBI) is declared toseamlessly reproduce the stream interleaved with the interleaved unitILVU as the smallest data unit, and contains an Interleaved Unit Flag(ILVU flag) identifying whether the corresponding video object unit VOBUis an interleaved block. The ILVU flag indicates whether the videoobject unit VOBU is in an interleaved block, and is set to 1 when it is.Otherwise the ILVU flag is set to 0.

[0267] When a video object unit VOBU is in an interleaved block, a UnitEND flag is declared to indicate whether the video object unit VOBU isthe last VOBU in the interleaved unit ILVU. Because the interleaved unitILVU is the data unit for continuous reading, the Unit END flag is setto 1 if the VOBU currently being read is the last VOBU in theinterleaved unit ILVU. Otherwise the Unit END flag is set to 0.

[0268] An Interleaved Unit End Address (ILVU_EA) identifying the addressof the last pack in the ILVU to which the VOBU belongs, and the startingaddress of the next interleaved unit ILVU, Next Interleaved Unit StartAddress (NT_ILVU_SA), are also declared when a video object unit VOBU isin an interleaved block. Both the Interleaved Unit End Address (ILVU_EA)and Next Interleaved Unit Start Address (NT_ILVU_SA) are expressed asthe number of sectors from the navigation pack NV of that VOBU.

[0269] When two system streams are seamlessly connected but the audiocomponents of the two system streams are not contiguous, particularlyimmediately before and after the seam, it is necessary to pause theaudio output to synchronize the audio and video components of the systemstream following the seam. Note that non-contiguous audio may resultfrom different audio signals being recording with the correspondingvideo blocks. With an NTSC signal, for example, the video frame cycle isapproximately 33. 33 msec while the AC-3 audio frame cycle is 32 msec.

[0270] To enable this resynchronization, audio reproduction stoppingtimes 1 and 2, i.e., Audio Stop PTM 1 in VOB (VOB_A_STP_PTM1), and AudioStop PTM2 in VOB (VOB_A_STP_PTM2), indicating the time at which theaudio is to be paused; and audio reproduction stopping periods 1 and 2,i.e., Audio Gap Length 1 in VOB (VOB_A_GAP_LEN1) and Audio Gap Length 2in VOB (VOB_A_GAP_LEN2), indicating for how long the audio is tobepaused, are also declared in the DSI packet. Note that-these times arespecified at the system clock precision (90 Khz).

[0271] The Angle Information for Seamless playback (SML_AGLI) declaresthe read start address when the angle is changed. Note that this fieldis valid when seamless, multi-angle control is enabled. This address isalso expressed as the number of sectors from the navigation pack NV ofthat VOBU. Because there are nine or fewer angles, there are nine angleaddress declaration cells: Destination Address of Angle Cell #1 forSeamless playback (SML_AGL_C1_DSTA) to Destination Address of Angle Cell#9 for Seamless playback (SML_AGL_C9_DSTA).

[0272] Note also that each title is edited in video object (VOB) units.Interleaved video objects (interleaved title editing units) arereferenced as “VOBS”; and the encoded range of the source data is theencoding unit.

[0273] DVD Encoder

[0274] A preferred embodiment of a digital video disk system authoringencoder ECD in which the multimedia bitstream authoring system accordingto the present invention is applied to a digital video disk system isdescribed below and shown in FIG. 25. It will be obvious that theauthoring encoder ECD applied to the digital video disk system, referredto below as a DVD encoder, is substantially identical to the authoringencoder EC shown in FIG. 2. The basic difference between these encodersis the replacement in the DVD encoder ECD of the video zone formatter1300 of the authoring encoder EC above with a VOB buffer 1000 andformatter 1100. It will also be obvious that the bitstream encoded bythis DVD encoder ECD is recorded to a digital video disk medium M. Theoperation of this DVD encoder ECD is therefore described below incomparison with the authoring encoder EC described above.

[0275] As in the above authoring encoder EC, the encoding systemcontroller 200 generates control signals St9, St11, St13, St21, St23,St25, St33, and St39 based on the scenario data St7 describing theuser-defined editing instructions input from the scenario editor 100,and controls the video encoder 300, sub-picture encoder 500, and audioencoder 700 in the DVD encoder ECD. Note that the user-defined editinginstructions in the DVD encoder ECD are a superset of the editinginstructions of the authoring encoder EC described above.

[0276] Specifically, the user-defined editing instructions (scenariodata St7) in the DVD encoder ECD similarly describe what source data isselected from all or a subset of the source data containing pluraltitles within a defined time period, and how the selected source data isreassembled to reproduce the scenario (sequence) intended by the user.The scenario data St7 of the DVD encoder ECD, however, further containssuch information as: the number of streams contained in the editingunits, which are obtained by splitting a multi-title source stream intoblocks at a constant time interval; the number of audio and sub-picturedata cells contained in each stream, and the sub-picture display timeand period; whether the title is a multi-rated title enabling parentallock control; whether the user content is selected from plural streamsincluding, for example, multiple viewing angles; and the method ofconnecting scenes when the angle is switched among the multiple viewingangles.

[0277] The scenario data St7 of the DVD encoder ECD also containscontrol information on a video object VOB unit basis. This informationis required to encode the media source stream, and specifically includessuch information as whether there are multiple angles or parentalcontrol features. When multiple angle viewing is enabled, the scenariodata St7 also contains the encoding bit rate of each stream consideringdata interleaving and the disk capacity, the start and end times of eachcontrol, and whether a seamless connection should be made between thepreceding and following streams.

[0278] The encoding system controller 200 extracts this information fromthe scenario data St7, and generates the encoding information table andencoding parameters required for encoding control. The encodinginformation table and encoding parameters are described with referenceto FIGS. 27, 28, and 29 below.

[0279] The stream encoding data St33 contains the system stream encodingparameters and system encoding start and end timing values required bythe DVD system to generate the VOBs. These system stream encodingparameters include the conditions for connecting one video object VOBwith those before and after, the number of audio streams, the audioencoding information and audio Ids, the number of sub-pictures and thesub-picture Ids, the video playback starting time information V-PTS, andthe audio playback starting time information APTS.

[0280] The title sequence control signal St39 supplies the multimediabitstream MBS formatting start and end timing information and formattingparameters declaring the reproduction control information and interleaveinformation.

[0281] Based on the video encoding parameter and encoding start/endtiming signal St9, the video encoder 300 encodes a specific part of thevideo stream St1 to generate an elementary stream conforming to theMPEG2 Video standard defined in ISO-13818. This elementary stream isoutput to the video stream buffer 400 as encoded video stream St15.

[0282] Note that while the video encoder 300 generates an elementarystream conforming to the MPEG2 Video standard defined in ISO-13818,specific encoding parameters are input via the video encoding parametersignal St9, including the encoding start and end timing, bit rate, theencoding conditions for the encoding start and end, the material type,including whether the material is an NTSC or PAL video signal ortelecine converted material, and whether the encoding mode is set foreither open GOP or closed GOP encoding.

[0283] The MPEG2 coding method is basically an interframe coding methodusing the correlation between frames for maximum signal compression,i.e., the frame being coded (the target frame) is coded by referencingframes before and/or after the target frame. However, intra-codedframes, i.e., frames that are coded based solely on the content of thetarget frame, are also inserted to avoid error propagation and enableaccessibility from mid-stream (random access). The coding unitcontaining at least one intra-coded frame (“intra-frame”) is called agroup_of_pictures GOP.

[0284] A group_of_pictures GOP in which coding is closed completelywithin that GOP is known as a “closed GOP.” A group_of_pictures GOPcontaining a frame coded with reference to a frame in a preceding orfollowing (ISO-13818 DOES NOT LIMIT P- and B-picture CODING toreferencing PAST frames) group_of_pictures GOP is an “open GOP.” It istherefore possible to playback a closed GOP using only that GOP.Reproducing an open GOP, however, also requires the presence of thereferenced GOP, generally the GOP preceding the open GOP.

[0285] The GOP is often used as the access unit. For example, the GOPmay be used as the playback start point for reproducing a title from themiddle, as a transition point in a movie, or for fast-forward play andother special reproduction modes. High speed reproduction can beachieved in such cases by reproducing only the intra-frame coded framesin a GOP or by reproducing only frames in GOP units.

[0286] Based on the sub-picture stream encoding parameter signal St11,the sub-picture encoder 500 encodes a specific part of the sub-picturestream St3 to generate a variable length coded bitstream of bitmappeddata. This variable length coded bitstream data is output as the encodedsub-picture stream St17 to the sub-picture stream buffer 600.

[0287] Based on the audio encoding parameter signal St13, the audioencoder 700 encodes a specific part of the audio stream St5 to generatethe encoded audio data. This encoded audio data may be data based on theMPEG1 audio standard defined in ISO-11172 and the MPEG2 audio standarddefined in ISO-13818, AC-3 audio data, or PCM (LPCM) data. Note that themethods and means of encoding audio data according to these standardsare known and commonly available.

[0288] The video stream buffer 400 is connected to the video encoder 300and to the encoding system controller 200. The video stream buffer 400stores the encoded video stream St15 input from the video encoder 300,and outputs the stored encoded video stream St15 as the time-delayedencoded video stream St27 based on the timing signal St21 supplied fromthe encoding system controller 200.

[0289] The sub-picture stream buffer 600 is similarly connected to thesub-picture encoder 500 and to the encoding system controller 200. Thesub-picture stream buffer 600 stores the encoded sub-picture stream St17input from the sub-picture encoder 500, and then outputs the storedencoded sub-picture stream St17 as time-delayed encoded sub-picturestream St29 based on the timing signal St23 supplied from the encodingsystem controller 200.

[0290] The audio stream buffer 800 is similarly connected to the audioencoder 700 and to the encoding system controller 200. The audio streambuffer 800 stores the encoded audio stream St19 input from the audioencoder 700, and then outputs the encoded audio stream St19 as thetime-delayed encoded audio stream St31 based on the timing signal St25supplied from the encoding system controller 200.

[0291] The system encoder 900 is connected to the video stream buffer400, sub-picture stream buffer 600, audio stream buffer 800, and theencoding system controller 200, and is respectively supplied therebywith the time-delayed encoded video stream St27, time-delayed encodedsub-picture stream St29, time-delayed encoded audio stream St31, and thesystem stream encoding parameter data St33. Note that the system encoder900 is a multiplexer that multiplexes the time-delayed streams St27,St29, and St31 based on the stream encoding data St33 (timing signal) togenerate title editing units (VOBs) St35.

[0292] The VOB buffer 1000 temporarily stores the video objects VOBsproduced by the system encoder 900. The formatter 1100 reads the delayedvideo objects VOB from the VOB buffer 1000 based on the title sequencecontrol signal St39 to generate one video zone VZ, and adds the volumefile structure VFS to generate the edited multimedia stream data St43.

[0293] The multimedia bitstream MBS St43 edited according to theuser-defined scenario is then sent to the recorder 1200. The recorder1200 processes the edited multimedia stream data St43 to the data streamSt45 format of the recording medium M, and thus records the formatteddata stream St45 to the recording medium M.

[0294] DVD Decoder

[0295] A preferred embodiment of a digital video disk system authoringdecoder DCD in which the multimedia bitstream authoring system of thepresent invention is applied to a digital video disk system is describedbelow and shown in FIG. 26. The authoring decoder DCD applied to thedigital video disk system, referred to below as a DVD decoder DCD,decodes the multimedia bitstream MBS edited using the DVD encoder ECD ofthe present invention, and recreates the content of each title accordingto the user-defined scenario. It will also be obvious that themultimedia bitstream St45 encoded by this DVD encoder ECD is recorded toa digital video disk medium M.

[0296] The basic configuration of the DVD decoder DCD according to thisembodiment is the same as that of the authoring decoder DC shown in FIG.3. The differences are that a different video decoder 3801 (shown as3800 in FIG. 26) is used in place of the video decoder 3800, and areordering buffer 3300 and selector 3400 are disposed between the videodecoder 3801 and synthesizer 3500.

[0297] Note that the selector 3400 is connected to the synchronizer2900, and is controlled by a switching signal St103.

[0298] The operation of this DVD decoder DCD is therefore describedbelow in comparison with the authoring decoder DC described above.

[0299] As shown in FIG. 26, the DVD decoder DCD comprises a multimediabitstream producer .2000, scenario selector 2100, decoding systemcontroller 23Q0, stream buffer 2400, system decoder 2500, video buffer2600, sub-picture buffer 2700, audio buffer 2800, synchronizer 2900,video decoder 3801, reordering buffer 3300, sub-picture decoder 3100,audio decoder 3200, selector 3400, synthesizer 3500, video data outputterminal 3600, and audio data output terminal 3700.

[0300] The bitstream producer 2000 comprises a recording media driveunit 2004 for driving the recording medium M; a reading head 2006 forreading the information recorded to the recording medium M and producingthe binary read signal St57; a signal processor 2008 for variouslyprocessing the read signal St57 to generate the reproduced bitstreamSt61; and a reproduction controller 2002.

[0301] The reproduction controller 2002 is connected to the decodingsystem controller 2300 from which the multimedia bitstream reproductioncontrol signal St53 is supplied, and in turn generates the reproductioncontrol signals St55 and St59 respectively controlling the recordingmedia drive unit (motor) 2004 and signal processor 2008.

[0302] So that the user-defined video, sub-picture, and audio portionsof the multimedia title edited by the authoring encoder EC arereproduced, the authoring decoder DC comprises a scenario selector 2100for selecting and reproducing the corresponding scenes (titles). Thescenario selector 2100 then outputs the selected titles as scenario datato the DVD decoder DCD.

[0303] The scenario selector 2100 preferably comprises a keyboard, CPU,and monitor. Using the keyboard, the user then inputs the desiredscenario based on the content of the scenario input by the DVD encoderECD. Based on the keyboard input, the CPU generates the scenarioselection data St51 specifying the selected scenario. The scenarioselector 2100 is connected to the decoding system controller 2300 by aninfrared communications device, for example, and inputs the generatedscenario selection data St51 to the decoding system controller 2300.

[0304] The stream buffer 2400 has a specific buffer capacity used totemporarily store the reproduced bitstream St61 input from the bitstreamproducer 2000, extract the volume file structure VFS, the initialsynchronization data SCR (system clock reference) in each pack, and theVOBU control information (DSI) in the navigation pack NV, to generatethe bitstream control data St63. The stream buffer 2400 is alsoconnected to the decoding system controller 2300, to which it suppliesthe generated bitstream control data St63.

[0305] Based on the scenario selection data St51 supplied by thescenario selector 2100, the decoding system controller 2300 thengenerates the bitstream reproduction control signal St53 controlling theoperation of the bitstream producer 2000. The decoding system controller2300 also extracts the user-defined playback instruction data from thebitstream reproduction control signal St53, and generates the decodinginformation table required for decoding control. This decodinginformation table is described further below with reference to FIGS. 26and 32. The decoding system controller 2300 also extracts the titleinformation recorded to the optical disk M from the file data structurearea FDS of the bitstream control data St63 to generate the titleinformation signal St200. Note that the extracted title informationincludes the video manager VMG, VTS information VTSI, the PGCinformation entries C_PBI #j, and the cell presentation time C_PBTM.

[0306] Note that the bitstream control data St63 is generated in packunits as shown in FIG. 19, and is supplied from the stream buffer 2400to the decoding system controller 2300, to which the stream buffer 2400is connected.

[0307] The synchronizer 2900 is connected to the decoding systemcontroller 2300 from which it receives the system clock reference SCRcontained in the synchronization control data St81 to set the internalsystem clock STC and supply the reset system clock St79 to the decodingsystem controller 2300.

[0308] Based on this system clock St79, the decoding system controller2300 also generates the stream read signal St65 at a specific intervaland outputs the read signal St65 to the stream buffer 2400. Note thatthe read unit in this case is the pack.

[0309] The method of generating the stream read signal St65 is describednext.

[0310] The decoding system controller 2300 compares the system clockreference SCR contained in the stream control data extracted from thestream buffer 2400 with the system clock St79 supplied from thesynchronizer 2900, and generates the read request signal St65 when thesystem clock St79 is greater than the system clock reference SCR of thebitstream control data St63. Pack transfers are controlled by executingthis control process on a pack unit.

[0311] Based on the scenario selection data St51, the decoding systemcontroller 2300 generates the decoding signal St69 defining the streamIds for the video, sub-picture, and audio bitstreams corresponding tothe selected scenario, and outputs to the system decoder 2500.

[0312] When a title contains plural audio tracks, e.g. audio tracks inJapanese, English, French, and/or other languages, and pluralsub-picture tracks for subtitles in Japanese, English, French, and/orother languages, for example, a discrete ID is assigned to each of thelanguage tracks. As described above with reference to FIG. 19, a streamID is assigned to the video data and MPEG audio data, and a substream IDis assigned to the sub-picture data, AC-3 audio data, linear PCM data,and navigation pack NV information. While the user need never be awareof these ID numbers, the user can select the language of the audioand/or subtitles using the scenario selector 2100. If English languageaudio is selected, for example, the ID corresponding to the Englishaudio track is sent to the decoding system controller 2300 as scenarioselection data St51. The decoding system controller 2300 then adds thisID to the decoding signal St69 output to the system decoder 2500.

[0313] Based on the instructions contained in the decoding signal St69,the system decoder 2500 respectively outputs the video, sub-picture, andaudio bitstreams input from the stream buffer 2400 to the video buffer2600, sub-picture buffer 2700, and audio buffer 2800 as the encodedvideo stream St71, encoded sub-picture stream St73, and encoded audiostream St75. Thus, when the stream ID input from the scenario selector2100 and the pack ID input from the stream buffer 2400 match, the systemdecoder 2500 outputs the corresponding packs to the respective buffers(i.e., the video buffer 2600, sub-picture buffer 2700, and audio buffer2800).

[0314] The system decoder 2500 detects the presentation time stamp PTSand decoding time stamp DTS of the smallest control unit in eachbitstream St67 to generate the time information signal St77. This timeinformation signal St77 is supplied to the synchronizer 2900 through thedecoding system controller 2300 as the synchronization control datast81.

[0315] Based on this synchronization control data St81, the synchronizer2900 determines the decoding start timing whereby each of the bitstreamswill be arranged in the correct sequence after decoding, and thengenerates and inputs the video stream decoding start signal St89 to thevideo decoder 3801 based on this decoding timing. The synchronizer 2900also generates and supplies the sub-picture decoding start signal St91and audio stream decoding start signal St93 to the sub-picture decoder3100 and audio decoder 3200, respectively.

[0316] The video decoder 3801 generates the video output request signalSt84 based on the video stream decoding start signal St89, and outputsto the video buffer 2600. In response to the video output request signalSt84, the video buffer 2600 outputs the video stream St83 to the videodecoder 3801. The video decoder 3801 thus detects the presentation timeinformation contained in the video stream St83, and disables the videooutput request signal St84 when the length of the received video streamSt83 is equivalent to the specified presentation time. A video streamequal in length to the specified presentation time is thus decoded bythe video decoder 3801, which outputs the reproduced video signal St95to the reordering buffer 3300 and selector 3400.

[0317] Because the encoded video stream is coded using the interframecorrelations between pictures, the coded order and display order do notnecessarily match on a frame unit basis. The video cannot, therefore, bedisplayed in the decoded order. The decoded frames are thereforetemporarily stored to the reordering buffer 3300. The synchronizer 2900therefore controls the switching signal St103 so that the reproducedvideo signal St95 output from the video decoder 3800 and the reorderingbuffer output St97 are appropriately selected and output in the displayorder to the synthesizer 3500.

[0318] The sub-picture decoder 3100 similarly generates the sub-pictureoutput request signal St86 based on the sub-picture decoding startsignal St91, and outputs to the sub-picture buffer 2700. In response tothe sub-picture output request signal. St86, the sub-picture buffer 2700outputs the sub-picture stream St85 to the sub-picture decoder 3100.Based on the presentation time information contained in the sub-picturestream St85, the sub-picture decoder 3100 decodes a length of thesub-picture stream St85 corresponding to the specified presentation timeto reproduce and supply to the synthesizer 3500 the sub-picture signalSt99.

[0319] The synthesizer 3500 superimposes the selector 3400 output withthe sub-picture signal St99 to generate and output the video signalStlO5 to the video data output terminal 3600.

[0320] The audio decoder 3200 generates and supplies to the audio buffer2800 the audio output request signal St88 based on the audio streamdecoding start signal St93. The audio buffer 2800 thus outputs the audiostream St87 to the audio decoder 3200. The audio decoder 3200 decodes alength of the audio stream St87 corresponding to the specifiedpresentation time based on the presentation time information containedin the audio stream St87, and outputs the decoded audio stream St101 tothe audio data output terminal 3700.

[0321] It is thus possible to reproduce a user-defined multimediabitstream MBS in real-time according to a user-defined scenario. Morespecifically, each time the user selects a different scenario, the DVDdecoder DCD is able to reproduce the title content desired by the userin the desired sequence by reproducing the multimedia bitstream MBScorresponding to the selected scenario.

[0322] It should be noted that the decoding system controller 2300 maysupply the title information signal St200 to the scenario selector 2100by means of the infrared communications device mentioned above oranother means. Interactive scenario selection controlled by the user canalso be made possible by the scenario selector 2100 extracting the titleinformation recorded to the optical disk M from the file data structurearea FDS of the bitstream control data St63 contained in the titleinformation signal St200, and displaying this title information on adisplay for user selection.

[0323] Note, further, that the stream buffer 2400, video buffer 2600,sub-picture buffer 2700, audio buffer 2800, and reordering buffer 3300are expressed above and in the figures as separate entities because theyare functionally different. It will be obvious, however, that a singlebuffer memory can be controlled to provide the same discretefunctionality by time-share controlled use of a buffer memory with anoperating speed plural times faster than the read and write rates ofthese separate buffers.

[0324] Multi-scene Control

[0325] The concept of multiple angle scene control according to thepresent invention is described below with reference to FIG. 21. Asdescribed above, titles that can be played back with numerous variationsare constructed from basic scene periods containing data common to eachtitle, and multi-scene periods comprising groups of different scenescorresponding to the various scenario requests. In FIG. 21, scenes 1, 5,and 8 are the common scenes of the basic scene periods. The multi-anglescenes (angles 1, 2, and 3) between scenes 1 and 5, and the parentallocked scenes (scenes 6 and 7) between scenes 5 and 8, are themulti-scene periods.

[0326] Scenes taken from different angles, i.e., angles 1, 2, and 3 inthis example, can be dynamically selected and reproduced during playbackin the multi-angle scene period. In the parental locked scene period,however, only one of the available scenes, scenes 6 and 7, havingdifferent content can be selected, and must be selected staticallybefore playback begins.

[0327] Which of these scenes from the multi-scene periods is to beselected and reproduced is defined by the user operating the scenarioselector 2100 and thereby generating the scenario selection data St51.In scenario 1 in FIG. 21 the user can freely select any of themulti-angle scenes, and scene 6 has been preselected for output in theparental locked scene period. Similarly in scenario 2, the user canfreely select any of the multi-angle scenes, and scene 7 has beenpreselected for output in the parental locked scene period.

[0328] With reference to FIGS. 30 and 31, furthermore, the contents ofthe program chain information VTS_PGCI is described. In FIG. 30, thecase that a scenario requested by the user is shown with respect to aVTSI data construction. The scenario 1 and scenario 2 shown in FIG. 21are described as program chain information VTS_PGC#1 and VTS_PGC#2.VTS_PGC#1 describing the scenario 1 consists of cell playbackinformation C_PBI#1 corresponding to scene 1, C_PBI#2, C_PBI#3, andC_PBI#4 within a multi-angle cell block, C_PBI#5 corresponding to scene5, C_PBI#6 corresponding to scene 6, and C_PBI#7 corresponding to scene8.

[0329] VTS PGCI#2 describing the scenario 2 consists of cell playbackinformation C_PBI#1 corresponding to scene 1, C_PBI#2, C_PBI#3, andC_PBI#4 within a multi-angle cell block corresponding to a multi-anglescene, C_PBI#5 corresponding to scene 5, C_PBI#6 corresponding to scene7, and C_PBI#7 corresponding to scene 8. According to the digital videosystem data structure, a scene which is a control unit of a scenario isdescribed as a cell which is a unit thereunder, thus a scenariorequested by a user can be obtained.

[0330] In FIG. 31, the case that a scenario requested by the user shownin FIG. 21 is shown with respect to a VOB data construction VTSTT_VOBS.As specifically shown in FIG. 31, the two scenarios 1 and 2 use the sameVOB data in common. With respect to a single scene commonly owned byeach scenario, VOB#1 corresponding to scene 1, VOB#5 corresponding toscene 5, and VOB#8 corresponding to scene 8 are arranged innon-interleaved block which is the contiguous block.

[0331] With respect to the multi-angle data commonly owned by scenarios1 and 2, one angle scene data is constructed by a single VOB.Specifically speaking, angle 1 is constructed by VOB#2, and angle 2 isconstructed by VOB#3, angle 3 is constructed by VOB#4. Thus constructedmulti-angle data is formed as the interleaved block for the sake ofswitching between each angle and seamless reproduction of each angledata. Scenes 6 and 7 peculiar to scenarios 1 and 2, respectively, areformed as the interleaved block for the sake of seamless reproductionbetween common scenes before and behind thereof as well as seamlessreproduction between each scene.

[0332] As described in the above, the user's requesting scenario shownin FIG. 21 can be realized by utilizing the video title playback controlinformation shown in FIG. 30 and the title playback VOB data structureshown in FIG. 31.

[0333] Seamless Playback

[0334] The seamless playback capability briefly mentioned above withregard to the digital video disk system data structure is describedbelow. Note that seamless playback refers to the reproduction in adigital video disk system of multimedia data including video, audio, andsub-picture data without intermittent breaks in the data or informationbetween basic scene periods, between basic scene periods and multi-sceneperiods, and between multi-scene periods.

[0335] Hardware factors contributing to intermittent playback of thisdata and title content include decoder underflow, i.e., an imbalancebetween the source data input speed and the decoding speed of the inputsource data.

[0336] Other factors relate to the properties of the playback data. Whenthe playback data is data that must be continuously reproduced for aconstant time unit in order for the user to understand the content orinformation, e.g., audio data, data continuity is lost when the requiredcontinuous presentation time cannot be assured. Reproduction of suchinformation whereby the required continuity is assured is referred to as“contiguous information reproduction,” or “seamless informationreproduction.” Reproduction of this information when the requiredcontinuity cannot be assured is referred to as “non-continuousinformation reproduction,” or “non-seamless information reproduction.”It is obvious that continuous information reproduction andnon-continuous information reproduction are, respectively, seamless andnon-seamless reproduction.

[0337] Note that seamless reproduction can be further categorized asseamless data reproduction and seamless information reproduction.Seamless data reproduction is defined as preventing physical blanks orinterruptions in the data playback (intermittent reproduction) as aresult of a buffer underflow state, for example. Seamless informationreproduction is defined as preventing apparent interruptions in theinformation when perceived by the user (intermittent presentation) whenrecognizing information from the playback data where there are no actualphysical breaks in the data reproduction. The specific method enablingseamless reproduction as thus described is described later below withreference to FIGS. 23 and 24.

[0338] Interleaving

[0339] The DVD data system streams described above are recorded using anappropriate authoring encoder EC as a movie or other multimedia title ona DVD recording medium. Note that the following description refers to amovie as the multimedia title being processed, but it will be obviousthat the invention shall not be so limited.

[0340] Supplying a single movie in a format enabling the movie to beused in plural different cultural regions or countries requires thescript to be recorded in the various languages used in those regions orcountries. It may even necessitate editing the content to conform to themores and moral expectations of different cultures. Even using such alarge-capacity storage system as the DVD system, however, it isnecessary to reduce the bit rate, and therefore the image quality, ifplural full-length titles edited from a single common source title arerecorded to a single disk. This problem can be solved by recording thecommon parts of plural titles only once, and recording the segmentsdifferent in each title for each different title only. This method makesit possible to record plural titles for different countries or culturesto a single optical disk without reducing the bit rate, and, therefore,retaining high image quality.

[0341] As shown in FIG. 21, the titles recorded to a single optical diskcontain basic scene periods of scenes common to all scenarios, andmulti-scene periods containing scenes specific to certain scenarios, toprovide parental lock control and multi-angle scene control functions.

[0342] In the case of the parental lock control function, titlescontaining sex scenes, violent scenes, or other scenes deemed unsuitablefor children, i.e., so-called “adult scenes,” are recorded with acombination of common scenes, adult scenes, and children's scenes. Thesetitle streams are achieved by arraying the adult and children's scenesto multi-scene periods between the common basic scene periods.

[0343] Multi-angle control can be achieved in a conventionalsingle-angle title by recording plural multimedia scenes obtained byrecording the subjects from the desired plural camera angles to themulti-scene periods arrayed between the common basic scene periods.Note, however, that while these plural scenes are described here asscenes recorded from different camera angles (positions), it will beobvious that the scenes may be recorded from the same camera angle butat different times, data generated by computer graphics, or other videodata.

[0344] When data is shared between different scenarios of a singletitle, it is obviously necessary to move the laser beam LS from thecommon scene data to the non-common scene data during reproduction,i.e., to move the optical pickup to a different position on the DVDrecording medium RC1. The problem here is that the time required to movethe optical pickup makes it difficult to continue reproduction withoutcreating breaks in the audio or video, i.e., to sustain seamlessreproduction. This problem can be theoretically solved by providing atrack buffer (stream buffer 2400) to delay data output an amountequivalent to the worst access time. In general, data recorded to anoptical disk is read by the optical pickup, appropriately processed, andtemporarily stored to the track buffer. The stored data is subsequentlydecoded and reproduced as video or audio data.

[0345] To thus enable the user to selectively excise scenes and choosefrom among plural scenes, a state wherein non-selected scene data isrecorded inserted between common scene data and selective scene datanecessarily occurs because the data units associated with individualscenes are contiguously recorded to the recording tracks of therecording medium. If data is then read in the recorded sequence,non-selected scene data must be accessed before accessing and decodingthe selected scene data, and seamless connections with the selectedscene is difficult. The excellent random access characteristics of thedigital video disk system, however, make seamless connections with theselected scenes possible.

[0346] In other words, by splitting scene-specific data into pluralunits of a specified data size, and interleaving plural split data unitsfor different scenes in a predefined sequence that is recorded to diskwithin the jumping range whereby an data underflow state does not occur,it is possible to reproduce the selected scenes without datainterruptions by intermittently accessing and decoding the data specificto the selected scenes using these split data units. Seamless datareproduction is thereby assured.

[0347] Interleaved Block and Interleave Unit

[0348] The interleaving method enabling seamless data reproductionaccording to the present invention is described below with reference toFIG. 24. and FIG. 71. Shown in FIG. 24 is a case from which threescenarios may be derived, i.e., branching from one video object VOB-A toone of plural video objects VOB-B, VOB-C, and VOB-D, and then mergingback again to a single video object VOB-E. The actual arrangement ofthese blocks recorded to a data recording track TR on disk is shown inFIG. 71.

[0349] Referring to FIG. 71, VOB-A and VOB-E are video objects withindependent playback start and end times, and are in principle arrayedto contiguous block regions. As shown in FIG. 24, the playback start andend times of VOBB, VOB-C, and VOB-D are aligned during interleaving. Theinterleaved data blocks are then recorded to disk to a contiguousinterleaved block region. The contiguous block regions and interleavedblock regions are then written to disk in the track path Dr direction inthe playback sequence. Plural video objects VOB, i.e., interleaved videoobjects VOBS, arrayed to the data recording track TR are shown in FIG.37.

[0350] Referring to FIG. 37, data regions to which data is continuouslyarrayed are called “blocks,” of which there are two types: “contiguousblock regions” in which VOB with discrete starting and end points arecontiguously arrayed, and “interleaved block regions” in which pluralVOB with aligned starting and end points are interleaved. The respectiveblocks are arrayed as shown in FIG. 38 in the playback sequence, i.e.,block 1, block 2, block 3, . . . block 7.

[0351] As shown in FIG. 73, the VTS title VOBS (VTSTT_VOBS) consist ofblocks 1-7, inclusive. Block 1 contains VOB 1 alone. Blocks 2, 3, 5, and7 similarly discretely contain VOBS 2, 3, 6, and 10. Blocks 2, 3, 5, and7 are thus contiguous block regions.

[0352] Block 4, however, contains VOB 4 and VOB 5 interleaved together,while block 6 contains VOB 7, VOB 8, and VOB 9 interleaved together.Blocks 4 and 6 are thus interleaved block regions.

[0353] The internal data structure of the contiguous block regions isshown in FIG. 73 with VOB-i and VOB-j arrayed as the contiguous blocksin the VOBs. As described with reference to FIG. 16, VOB-i and VOB-jinside the contiguous block regions are further logically divided intocells as the playback unit. Both VOB-i and VOB-j in this figure areshown comprising three cells CELL #1, CELL #2, and CELL #3.

[0354] Each cell comprises one or more video object unit VOBU with thevideo object unit VOBU defining the boundaries of the cell. Each cellalso contains information identifying the position of the cell in theprogram chain PGC (the playback control information of the digital videodisk system). More specifically, this position information is theaddress of the first and last VOBU in the cell. As also shown in FIG.73, these VOB and the cells defined therein are also recorded to acontiguous block region so that contiguous blocks are contiguouslyreproduced. Reproducing these contiguous blocks is therefore no problem.

[0355] The internal data structure of the interleaved block regions isshown in FIG. 74. In the interleaved block regions each video object VOBis divided into interleaved units ILVU, and the interleaved units ILVUassociated with each VOB are alternately arrayed. Cell boundaries aredefined independently of the interleaved units ILVU. For example, VOB-kis divided into four interleaved units ILVUk1, ILVUk2, ILVUk3, andILVUk4, and are confined by a single cell CELL#k. VOB-k is likewisedivided into four interleaved units ILVUm1, ILVUm2, ILVUm3, and ILVUm4,and is confined by a single cell CELL#m. Note that instead of a singlecell CELL#k or CELL#m, each of VOB-k and VOB-m can be divided into morethan two cells. The interleaved units ILVU thus contains both audio andvideo data.

[0356] In the example shown in FIG. 74, the interleaved units ILVUk1,ILVUk2, ILVUk3, and ILVUk4, and ILVUm1, ILVUm2, ILVUm3, and ILVUm4, fromtwo different video objects VOB-k and VOB-m are alternately arrayedwithin a single interleaved block. By interleaving the interleaved unitsILVU of two video objects VOB in this sequence, it is possible toachieve seamless reproduction branching from one scene to one of pluralscenes, and from one of plural scenes to one scene.

[0357] Multi-scene Control

[0358] The multi-scene period is described together with the concept ofmulti-scene control according to the present invention using by way ofexample a title comprising scenes recorded from different angles.

[0359] Each scene in multi-scene control is recorded from the sameangle, but may be recorded at different times or may even be computergraphics data. The multi-angle scene periods may therefore also becalled multi-scene periods.

[0360] Parental Control

[0361] The concept of recording plural titles comprising alternativescenes for such functions as parental lock control and recordingdirector's cuts is described below using FIG. 15.

[0362] An example of a multi-rated title stream providing for parentallock control is shown in FIG. 15. When so-called “adult scenes”containing sex, violence, or other scenes deemed unsuitable for childrenare contained in a title implementing parental lock control, the titlestream is recorded with a combination of common system streams SSa, SSb,and Sse, an adult-oriented system stream SSc containing the adultscenes, and a child-oriented system stream SSd containing only thescenes suitable for children. Title streams such as this are recorded asa multi-scene system stream containing the adult-oriented system streamSsc and the child-oriented system stream Ssd arrayed to the multi-sceneperiod between common system streams Ssb and Sse.

[0363] The relationship between each of the component titles and thesystem stream recorded to the program chain PGC of a title stream thuscomprised is described below.

[0364] The adult-oriented title program chain PGC1 comprises in sequencethe common system streams Ssa and Ssb, the adult-oriented system streamSsc, and the common system stream Sse. The child-oriented title programchain PGC2 comprises in sequence the common system streams Ssa and Ssb,the child-oriented system stream Ssd, and the common system stream Sse.

[0365] By thus arraying the adult-oriented system stream Ssc andchild-oriented system stream Ssd to a multi-scene period, the decodingmethod previously described can reproduce the title containingadult-oriented content by reproducing the common system streams Ssa andSsb, then selecting and reproducing the adult-oriented system streamSsc, and then reproducing the common system stream Sse as instructed bythe adult-oriented title program chain PGC1. By alternatively followingthe child-oriented title program chain PGC2 and selecting thechild-oriented system stream Ssd in the multi-scene period, achild-oriented title from which the adult-oriented scenes have beenexpurgated can be reproduced.

[0366] This method of providing in the title stream a multi-scene periodcontaining plural alternative scenes, selecting which of the scenes inthe multi-scene period are to be reproduced before playback begins, andgenerating plural titles containing essentially the same title contentbut different scenes in part, is called parental lock control.

[0367] Note that parental lock control is so named because of theperceived need to protect children from undesirable content. From theperspective of system stream processing, however, parental lock controlis a technology for statically generating different title streams bymeans of the user pre-selecting specific scenes from a multi-sceneperiod. Note, further, that this contrasts with multi-angle scenecontrol, which is a technology for dynamically changing the content of asingle title by means of the user selecting scenes from the multi-sceneperiod freely and in real-time during title playback.

[0368] This parental lock control technology can also be used to enabletitle stream editing such as when making the director's cut. Thedirector's cut refers to the process of editing certain scenes from amovie to, for example, shorten the total presentation time. This may benecessary, for example, to edit a feature-length movie for viewing on anairplane where the presentation time is too long for viewing within theflight time or certain content may not be acceptable. The movie directorthus determines which scenes may be cut to shorten the movie. The titlecan then be recorded with both a full-length, unedited system stream andan edited system stream in which the edited scenes are recorded tomulti-scene periods. At the transition from one system stream to anothersystem stream in such applications, parental lock control must be ableto maintain smooth playback image output. More specifically, seamlessdata reproduction whereby a data underflow state does not occur in theaudio, video, or other buffers, and seamless information reproductionwhereby no unnatural interruptions are audibly or visibly perceived inthe audio and video playback, are necessary.

[0369] Multi-angle CControl

[0370] The concept of multi-angle scene control in the present inventionis described next with reference to FIG. 33. In general, multimediatitles are obtained by recording both the audio and video information(collectively “recording” below) of the subject over time T. The angledscene blocks #SC1, #SM1, #SM2, #SM3, and #SC3 represent the multimediascenes obtained at recording unit times T1, T2, and T3 by recording thesubject at respective camera angles. Scenes #SM1, #SM2, and #SM3 arerecorded at mutually different (first, second, and third) camera anglesduring recording unit time T2, and are referenced below as the first,second, and third angled scenes.

[0371] Note that the multi-scene periods referenced herein are basicallyassumed to comprise scenes recorded from different angles. The scenesmay, however, be recorded from the same angle but at different times, orthey may be computer graphics data. The multi-angle scene periods arethus the multi-scene periods from which plural scenes can be selectedfor presentation in the same time period, whether or not the scenes areactually recorded at different camera angles.

[0372] Scenes #SC1 and #SC3 are scenes recorded at the same commoncamera angle during recording unit times T1 and T3, i.e., before andafter the multi-angle scenes. These scenes are therefore called “commonangle scenes.” Note that one of the multiple camera angles used in themulti-angle scenes is usually the same as the common camera angle.

[0373] To understand the relationship between these various angledscenes, multi-angle scene control is described below using a livebroadcast of a baseball game for example only.

[0374] The common angle scenes #SC1 and #SC3 are recorded at the commoncamera angle, which is here defined as the view from center field on theaxis through the pitcher, batter, and catcher.

[0375] The first angled scene #SM1 is recorded at the first multi-cameraangle, i.e., the camera angle from the backstop on the axis through thecatcher, pitcher, and batter. The second angled scene #SM2 is recordedat the second multi-camera angle, i.e., the view from center field onthe axis through the pitcher, batter, and catcher. Note that the secondangled scene #SM2 is thus the same as the common camera angle in thisexample. It therefore follows that the second angled scene #SM2 is thesame as the common angle scene #SC2 recorded during recording unit timeT2. The third angled scene #SM3 is recorded at the third multi-cameraangle, i.e., the camera angle from the backstop focusing on the infield.

[0376] The presentation times of the multiple angle scenes #SM1, #SM2,and #SM3 overlap in recording unit time T2; this period is called the“multi-angle scene period.” By freely selecting one of the multipleangle scenes #SM1, #SM2, and #SM3 in this multi-angle scene period, theviewer is able to change his or her virtual viewing position to enjoy adifferent view of the game as though the actual camera angle is changed.Note that while there appears to be a time gap between common anglescenes #SC1 and #SC3 and the multiple angle scenes #SM1, #SM2, and #SM3in FIG. 33, this is simply to facilitate the use of arrows in the figurefor easier description of the data reproduction paths reproduced byselecting different angled scenes. There is no actual time gap duringplayback.

[0377] Multi-angle scene control of the system stream based on thepresent invention is described next with reference to FIG. 23 from theperspective of connecting data blocks. The multimedia data correspondingto common angle scene #SC is referenced as common angle data BA, and thecommon angle data BA in recording unit times T1 and T3 are referenced asBA1 and BA3, respectively. The multimedia data corresponding to themultiple angle scenes #SM1, #SM2, and #SM3 are referenced as first,second, and third angle scene data MA1, MA2, and MA3. As previously'described with reference to FIG. 33, scenes from the desired angled canbe viewed by selecting one of the multiple angle data units MA1, MA2,and MA3. There is also no time gap between the common angle data BA1 andBA3 and the multiple angle data units MA1, MA2, and MA3.

[0378] In the case of an MPEG system stream, however, intermittentbreaks in the playback information can result between the reproducedcommon and multiple angle data units depending upon the content of thedata at the connection between the selected multiple angle data unitMA1, MA2, and MA3 and the common angle data BA (either the first commonangle data BA1 before the angle selected in the multi-angle scene periodor the common angle data BA3 following the angle selected in themulti-angle scene period). The result in this case is that the titlestream is not naturally reproduced as a single contiguous title, i.e.,seamless data reproduction is achieved but non-seamless informationreproduction results.

[0379] The multi-angle selection process whereby one of plural scenes isselectively reproduced from the multi-angle scene period with seamlessinformation presentation to the scenes before and after is describedbelow with application in a digital video disk system using FIG. 23.

[0380] Changing the scene angle, i.e., selecting one of the multipleangle data units MA1, MA2, and MA3, must be completed beforereproduction of the preceding common angle data BAl is completed. It isextremely difficult, for example, to change to a different angle dataunit MA2 during reproduction of common angle data BA1. This is becausethe multimedia data has a variable length coded MPEG data structure,which makes it difficult to find the data break points (boundaries) inthe selected data blocks. The video may also be disrupted when the angleis changed because inter-frame correlations are used in the codingprocess. The group_of_pictures GOP processing unit of the MPEG standardcontains at least one refresh frame, and closed processing notreferencing frames belonging to another GOP is possible within this GOPprocessing unit.

[0381] In other words, if the desired angle data, e.g., MA3, is selectedbefore reproduction reaches the multi-angle scene period, and at thelatest by the time reproduction of the preceding common angle data BA1is completed, the angle data selected from within the multi-angle sceneperiod can be seamlessly reproduced. However, it is extremely difficultwhile reproducing one angle to select and seamlessly reproduce anotherangle within the same multi-angle scene period. It is thereforedifficult when in a multi-angle scene period to dynamically select adifferent angle unit presenting, for example, a view from a differentcamera angle.

[0382] Flow Chart: Encoder

[0383] The encoding information table generated by the encoding systemcontroller 200 from information extracted from the scenario data St7 isdescribed below referring to FIG. 27.

[0384] The encoding information table contains VOB set data streamscontaining plural VOB corresponding to the scene periods beginning andending at the scene branching and connecting points, and VOB datastreams corresponding to each scene. These VOB set data streams shown inFIG. 27 are the encoding information tables generated at step #100 inFIG. 34 by the encoding system controller 200 for creating the DVDmultimedia stream based on the user-defined title content.

[0385] The user-defined scenario contains branching points from commonscenes to plural scenes, or connection points to other common scenes.The VOB corresponding to the scene period delimited by these branchingand connecting points is a VOB set, and the data generated to encode aVOB set is the VOB set data stream. The title number specified by theVOB set data stream is the title number TITLE_NO of the VOB set datastream.

[0386] The VOB Set data structure in FIG. 27 shows the data content forencoding one VOB set in the VOB set data stream, and comprises: the VOBset number VOBS_NO, the VOB number VOB_NO in the VOB set, the precedingVOB seamless connection flag VOB_Fsb, the following VOB seamlessconnection flag VOB_Fsf, the multi-scene flag VOB_Fp, the interleaveflag VOB_Fi, the multi-angle flag VOB_Fm, the multi-angle seamlessswitching flag VOB_FsV, the maximum bit rate of the interleaved VOBILV_BR, the number of interleaved VOB divisions ILV_DIV, and the minimuminterleaved unit presentation time ILVU_MT.

[0387] The VOB set number VOBS_NO is a sequential number identifying theVOB set and the position of the VOB set in the reproduction sequence ofthe title scenario.

[0388] The VOB number VOB_NO is a sequential number identifying the VOBand the position of the VOB in the reproduction sequence of the titlescenario.

[0389] The preceding VOB seamless connection flag VOB_Fsb indicateswhether a seamless connection with the preceding VOB is required forscenario reproduction.

[0390] The following VOB seamless connection flag VOB_Fsf indicateswhether there is a seamless connection with the following VOB duringscenario reproduction.

[0391] The multi-scene flag VOB_Fp identifies whether the VOB setcomprises plural video objects VOB.

[0392] The interleave flag VOB_Fi identifies whether the VOB in the VOBset are interleaved.

[0393] The multi-angle flag VOB_Fm identifies whether the VOB set is amulti-angle set.

[0394] The multi-angle seamless switching flag VOB_FsV identifieswhether angle changes within the multi-angle scene period are seamlessor not.

[0395] The maximum bit rate of the interleaved VOB ILV_BR defines themaximum bit rate of the interleaved VOBs.

[0396] The number of interleaved VOB divisions ILV_DIV identifies thenumber of interleave units in the interleaved VOB.

[0397] The minimum interleave unit presentation time ILVU_MT defines thetime that can be reproduced when the bit rate of the smallest interleaveunit at which a track buffer data underflow state does not occur is themaximum bit rate of the interleaved VOB ILV_BR during interleaved blockreproduction.

[0398] The encoding information table for each VOB generated by theencoding system controller 200 based on the scenario data St7 isdescribed below referring to FIG. 28. The VOB encoding parametersdescribed below and supplied to the video encoder 300, audio encoder700, and system encoder 900 for stream encoding are produced based onthis encoding information table.

[0399] The VOB data streams shown in FIG. 28 are the encodinginformation tables generated at step #100 in FIG. 34 by the encodingsystem controller 200 for creating the DVD multimedia stream based-onthe user-defined title content.

[0400] The encoding unit is the video object VOB, and the data generatedto encode each video object VOB is the VOB data stream. For example, aVOB set comprising three angle scenes comprises three video objects VOB.The data structure shown in FIG. 28 shows the content of the data forencoding one VOB in the VOB data stream.

[0401] The VOB data structure contains the video material start timeVOB_VST, the video material end time VOB_VEND, the video signal typeVOB_V_KIND, the video encoding bit rate V_BR, the audio material starttime VOB_AST, the audio material end time VOB_AEND, the audio codingmethod VOB_A_KIND, and the audio encoding bit rate A_BR.

[0402] The video material start time VOB_VST is the video encoding starttime corresponding to the time of the video signal.

[0403] The video material end time VOB_VEND is the video encoding endtime corresponding to the time of the video signal.

[0404] The video material type VOB_V_KIND identifies whether the encodedmaterial is in the NTSC or PAL format, for example, or is photographicmaterial (a movie, for example) converted to a television broadcastformat (so-called telecine conversion).

[0405] The video encoding bit rate V_BR is the bit rate at which thevideo signal is encoded.

[0406] The audio material start time VOB_AST is the audio encoding starttime corresponding to the time of the audio signal.

[0407] The audio material end time VOB_AEND is the audio encoding endtime corresponding to the time of the audio signal.

[0408] The audio coding method VOB_A_KIND identifies the audio encodingmethod as AC-3, MPEG, or linear PCM, for example.

[0409] The audio encoding bit rate A_BR is the bit rate at which theaudio signal is encoded.

[0410] The encoding parameters used by the video encoder 300,sub-picture encoder 500, and audio encoder 700, and system encoder 900for VOB encoding are shown in FIG. 29. The encoding parameters include:the VOB number VOB_NO, video encode start time V_STTM, video encode endtime V_ENDTM, the video encode mode V_ENCMD, the video encode bit rateV_RATE, the maximum video encode bit rate V_MRATE, the GOP structurefixing flag GOP_Fxflag, the video encode GOP structure GOPST, theinitial video encode data V_INTST, the last video encode data V_ENDST,the audio encode start time A_STTM, the audio encode end time A_ENDTM,the audio encode bit rate A_RATE, the audio encode method A_ENCMD, theaudio start gap A_STGAP, the audio end gap A_ENDGAP, the preceding VOBnumber B_VOB_NO, and the following VOB number F_VOB_NO.

[0411] The VOB number VOB_NO is a sequential number identifying the VOBand the position of the VOB in the reproduction sequence of the titlescenario.

[0412] The video encode start time V_STTM is the start time of videomaterial encoding.

[0413] The video encode end time V_ENDTM is the end time of videomaterial encoding.

[0414] The video encode mode V_ENCMD is an encoding mode for declaringwhether reverse telecine conversion shall be accomplished during videoencoding to enable efficient coding when the video material is telecineconverted material.

[0415] The video encode bit rate V_RATE is the average bit rate of videoencoding.

[0416] The maximum video encode bit rate V_MRATE is the maximum bit rateof video encoding.

[0417] The GOP structure fixing flag GOP_Fxflag specifies whetherencoding is accomplished without changing the GOP structure in themiddle of the video encoding process. This is a useful parameter fordeclaring whether seamless switch is enabled in a multi-angle sceneperiod.

[0418] The video encode GOP structure GOPST is the GOP structure datafrom encoding.

[0419] The initial video encode data V_INTST sets the initial value ofthe VBV buffer (decoder buffer) at the start of video encoding, and isreferenced during video decoding to initialize the decoding buffer. Thisis a useful parameter for declaring seamless reproduction with thepreceding encoded video stream.

[0420] The last video encode data V_ENDST sets the end value of the VBVbuffer (decoder buffer) at the end of video encoding, and is referencedduring video decoding to initialize the decoding buffer. This is auseful parameter for declaring seamless reproduction with the precedingencoded video stream.

[0421] The audio encode start time A_STTM is the start time of audiomaterial encoding.

[0422] The audio encode end time A_ENDTM is the end time of audiomaterial encoding.

[0423] The audio encode bit rate A_RATE is the bit rate used for audioencoding.

[0424] The audio encode method A3 ENCMD identifies the audio encodingmethod as AC-3, MPEG, or linear PCM, for example.

[0425] The audio start gap A_STGAP is the time offset between the startof the audio and video presentation at the beginning of a VOB. This is auseful parameter for declaring seamless reproduction with the precedingencoded system stream.

[0426] The audio end gap A_ENDGAP is the time offset between the end ofthe audio and video presentation at the end of a VOB. This is a usefulparameter for declaring seamless reproduction with the preceding encodedsystem stream.

[0427] The preceding VOB number B_VOB_NO is the VOB_NO of the precedingVOB when there is a seamlessly connected preceding VOB.

[0428] The following VOB number F_VOB_NO is the VOB_NO of the followingVOB when there is a seamlessly connected following VOB.

[0429] The operation of a DVD encoder ECD according to the presentinvention is. described below with reference to the flow chart in FIG.34. Note that the steps shown with a double line are subroutines. Itshould be obvious that while the operation described below relatesspecifically in this case to the DVD encoder ECD of the presentinvention, the operation described also applies to an authoring encoderEC.

[0430] At step #100, the user inputs the editing commands according tothe user-defined scenario while confirming the content of the multimediasource data streams St1, St2, and St3.

[0431] At step #200, the scenario editor 100 generates the scenario dataSt7 containing the above edit command information according to theuser's editing instructions.

[0432] When generating the scenario data St7 in step #200, the userediting commands related to multi-angle and parental lock multi-sceneperiods in which interleaving is presumed must be input to satisfy thefollowing conditions.

[0433] First, the VOB maximum bit rate must be set to assure sufficientimage quality, and the track buffer capacity, jump performance, jumptime, and jump distance of the DVD decoder DCD used as the reproductionapparatus of the DVD encoded data must be determined. Based on thesevalues, the reproduction time of the shortest interleaved unit isobtained from equations 3 and 4. Based on the reproduction time of eachscene in the multi-scene period, it must then be determined whetherequations 5 and 6 are satisfied. If equations 5 and 6 are not satisfied,the user must change the edit commands until equations 5 and 6 aresatisfied by, for example, connecting part of the following scene toeach scene in the multi-scene period.

[0434] When multi-angle edit commands are used, equation 7 must besatisfied for seamless switching, and edit commands matching the audioreproduction time with the reproduction time of each scene in each anglemust be entered. If non-seamless switching is used, the user must entercommands to satisfy equation 8.

[0435] At step #300, the encoding system controller 200 first determineswhether the target scene is to be seamlessly connected to the precedingscene based on the scenario data St7.

[0436] Note that when the preceding scene period is a multi-scene periodcomprising plural scenes but the presently selected target scene is acommon scene (not in a multi-scene period), a seamless connection refersto seamlessly connecting the target scene with any one of the scenescontained in the preceding multi-scene period. When the target scene isa multi-scene period, a seamless connection still refers to seamlesslyconnecting the target scene with any one of the scenes from the samemulti-scene period.

[0437] If step #300 returns NO, i.e., a non-seamless connection isvalid, the procedure moves to step #400.

[0438] At step #400, the encoding system controller 200 resets thepreceding VOB seamless connection flag VOB_Fsb indicating whether thereis a seamless connection between the target and preceding scenes. Theprocedure then moves to step #600.

[0439] On the other hand, if step #300 returns YES, i.e., there is aseamless connection to the preceding scene, the procedure moves to step#500.

[0440] At step #500 the encoding system controller 200 sets thepreceding VOB seamless connection flag VOB_Fsb. The procedure then movesto step #600.

[0441] At step #600 the encoding system controller 200 determineswhether there is a seamless connection between the target and followingscenes based on scenario data St7. If step #600 returns NO, i.e., anon-seamless connection is valid, the procedure moves to step #700.

[0442] At step #700, the encoding system controller 200 resets thefollowing VOB seamless connection flag VOB_Fsf indicating whether thereis a seamless connection with the following scene. The procedure thenmoves to step #900.

[0443] However, if step #600 returns YES, i.e., there is a seamlessconnection to the following scene, the procedure moves to step #800.

[0444] At step #800 the encoding system controller 200 sets thefollowing VOB seamless connection flag VOB Fsf. The procedure then movesto step #900.

[0445] At step #900 the encoding system controller 200 determineswhether there is more than connection target scene, i.e., whether amulti-scene period is selected, based on the scenario data St7. Aspreviously described, there are two possible control methods inmulti-scene periods: parental lock control whereby only one of pluralpossible reproduction paths that can be constructed from the scenes inthe multi-scene period is reproduced, and multi-angle control wherebythe reproduction path can be switched within the multi-scene period topresent different viewing angles.

[0446] If step #900 returns NO, i.e., there are not multiple scenes, theprocedure moves to step #1000.

[0447] At step #1000 the multi-scene flag VOB_Fp identifying whether theVOB set comprises plural video objects VOB (a multi-scene period isselected) is reset, and the procedure moves to step #1800 for encodeparameter production. This encode parameter production subroutine isdescribed below.

[0448] However, if step #900 returns YES, there is a multi-sceneconnection, the procedure moves to step #1100.

[0449] At step #1100, the multi-scene flag VOB_Fp is set, and theprocedure moves to step #1200 whereat it is judged whether a multi-angleconnection is selected, or not.

[0450] At step #1200 it is determined whether a change is made betweenplural scenes in the multi-scene period, i.e., whether a multi-anglescene period is selected. If step #1200 returns NO, i.e., no scenechange is allowed in the multi-scene period as parental lock controlreproducing only one reproduction path has been selected, the proceduremoves to step #1300.

[0451] At step #1300 the multi-angle flag VOB_Fm identifying whether thetarget connection scene is a multi-angle scene is reset, and theprocedure moves to step #1302.

[0452] At step #1302 it is determined whether either the preceding VOBseamless connection flag VOB Fsb or following VOB seamless connectionflag VOB_Fsf is set. If step #1302 returns YES, i.e., the targetconnection scene seamlessly connects to the preceding, the following, orboth the preceding and following scenes, the procedure moves to step#1304.

[0453] At step #1304 the interleave flag VOB_Fi identifying whether theVOB, the encoded data of the target scene, is interleaved is set. Theprocedure then moves to step #1800.

[0454] However, if step #1302 returns NO, i.e., the target connectionscene does not seamlessly connect to the preceding or following scene,the procedure moves to step #1306.

[0455] At step #1306 the interleave flag VOB_Fi is reset, and theprocedure moves to step #1800.

[0456] If step #1200 returns YES, however, i. e., there is a multi-angleconnection, the procedure moves to step #1400.

[0457] At step #1400, the multi-angle flag VOB_Fm and interleave flagVOB_FI are set, and the procedure moves to step #1500.

[0458] At step #1500 the encoding system controller 200 determineswhether the audio and video can be seamlessly switched in a multi-anglescene period, i.e., at a reproduction unit smaller than the VOB, basedon the scenario data St7. If step #1500 returns NO, i.e., non-seamlessswitching occurs, the procedure moves to step #1600.

[0459] At step #1600 the multi-angle seamless switching flag VOB_FsVindicating whether angle changes within the multi-angle scene period areseamless or not is reset, and the procedure moves to step #1800.

[0460] However, if step #1500 returns YES, i.e., seamless switchingoccurs, the procedure moves to step #1700.

[0461] At step #1700 the multi-angle seamless switching flag VOB_FsV isset, and the procedure moves to step #1800.

[0462] Therefore, as shown by the flow chart in FIG. 51, encodeparameter production (step #1800) is only begun after the editinginformation is detected from the above flag settings in the scenariodata St7 reflecting the user-defined editing instructions.

[0463] Based on the user-defined editing instructions detected from theabove flag settings in the scenario data St7, information is added tothe encoding information tables for the VOB Set units and VOB units asshown in FIGS. 27 and 28 to encode the source streams, and the encodingparameters of the VOB data units shown in FIG. 29 are produced, in step#1800. The procedure then moves to step #1900 for audio and videoencoding.

[0464] The encode parameter production steps (step #1800) are describedin greater detail below referring to FIGS. 52, 53, 54, and 55.

[0465] Based on the encode parameters produced in step #1800, the videodata and audio data are encoded in step #1900, and the procedure-movesto step #2000.

[0466] Note that the sub-picture data is normally inserted during videoreproduction on an as-needed basis, and contiguity with the precedingand following scenes is therefore not usually necessary. Moreover, thesub-picture data is normally video information for one frame, and unlikeaudio and video data having an extended time-base, sub-picture data isusually static, and is not normally presented continuously. Because thepresent invention relates specifically to seamless and non-seamlesscontiguous reproduction as described above, description of sub-picturedata encoding is omitted herein for simplicity.

[0467] Step #2000 is the last step in a loop comprising steps #300 tostep #2000, and causes this loop to be repeated as many times as thereare VOB Sets. This loop formats the program chain VTS_PGC#i to containthe reproduction sequence and other reproduction information for eachVOB in the title (FIG. 16) in the program chain data structure,interleaves the VOB in the multi-scene periods, and completes the VOBSet data stream and VOB data stream needed for system stream encoding.The procedure then moves to step #2100.

[0468] At step #2100 the VOB Set data stream is completed as theencoding information table by adding the total number of VOB SetsVOBS_NUM obtained as a result of the loop through step #2000 to the VOBSet data stream, and setting the number of titles TITLE_NO defining thenumber of scenario reproduction paths in the scenario data St7. Theprocedure then moves-to-step #2200.

[0469] System stream encoding producing the VOB (VOB#i) data in the VTStitle VOBS (VTSTT_VOBS) (FIG. 16) is accomplished in step #2200 based onthe encoded video stream and encoded audio stream output from step#1900, and the encode parameters in FIG. 29. The procedure then moves tostep #2300.

[0470] At step #2300 the VTS information VTSI, VTSI management tableVTSI_MAT, VTSPGC information table VTS_PGCIT, and the program chaininformation VTS_PGCI#i controlling the VOB data reproduction sequenceshown in FIG. 16 are produced, and formatting to, for example,interleave the VOB contained in the multi-scene periods, isaccomplished. The specific steps executed in this formatting operationare described below with reference to FIGS. 49, 50, 51, 52, and 53.

[0471] The encode parameter production subroutine shown as step #1800 inFIG. 34B is described next using FIGS. 52, 53, and 54 using by way ofexample the operation generating the encode parameters for multi-anglecontrol.

[0472] Starting from FIG. 35, the process for generating the encodeparameters of a non-seamless switching stream with multi-angle controlis described first. This stream is generated when step #1500 in FIG. 34returns NO and the following flags are set as shown: VOB_Fsb=1 orVOB_Fsf=1, VOB_Fp=1, VOB_Fi=1, VOB_Fm=1, and VOB_FsV=0.

[0473] The following operation produces the encoding information tablesshown in FIG. 27 and FIG. 28, and the encode parameters shown in FIG.29.

[0474] At step #1812, the scenario reproduction sequence (path)contained in the scenario data St7 is extracted, the VOB Set numberVOBS_NO is set, and the VOB number VOB_NO is set for one or more VOB inthe VOB Set.

[0475] At step #1814 the maximum bit rate ILV_BR of the interleaved VOBis extracted from the scenario data St7, and the maximum video encodebit rate V_MRATE from the encode parameters is set based on theinterleave flag VOB_Fi setting (=1).

[0476] At step #1816, the minimum interleaved unit presentation timeILVU_MT is extracted from the scenario data St7.

[0477] At step #1818, the video encode GOP structure GOPST values N=15and M=3 are set, and the GOP structure fixing flag GOP_Fxflag is set(=1), based on the multi-scene flag VOB_Fp setting (=1).

[0478] Step #1820 is the common VOB data setting routine, which isdescribed below referring to the flow chart in FIG. 36. This common VOBdata setting routine produces the encoding information tables shown inFIGS. 27 and 28, and the encode parameters shown in FIG. 29.

[0479] At step #1822 the video material start time VOB_VST and videomaterial end time VOB_VEND are extracted for each VOB, and the videoencode start time V_STTM and video encode end time V_ENDTM are used asvideo encoding parameters.

[0480] At step #1824 the audio material start time VOB_AST of each VOBis extracted from the scenario data St7, and the audio encode start timeA_STTM is set as an audio encoding parameter.

[0481] At step #1826 the audio material end time VOB_AEND is extractedfor each VOB from the scenario data St7, and at a time not exceeding theVOB_AEND time. This time extracted at an audio access unit (AAU) is setas the audio encode end time A_ENDTM which is an audio encodingparameter. Note that the audio access unit AAU is determined by theaudio encoding method.

[0482] At step #1828 the audio start gap A_STGAP obtained from thedifference between the video encode start time V_STTM and the audioencode start time A_STTM is defined as a system encode parameter.

[0483] At step #1830 the audio end gap A_ENDGAP obtained from thedifference between the video encode end time V_ENDTM and the audioencode end time A_ENDTM is defined as a system encode parameter.

[0484] At step #1832 the video encoding bit rate V_BR is extracted fromthe scenario data St7, and the video encode bit rate V_RATE, which isthe average bit rate of video encoding, is set as a video encodingparameter.

[0485] At step #1834 the audio encoding bit rate A_BR is extracted fromthe scenario data St7, and the audio encode bit rate A_RATE is set as anaudio encoding parameter.

[0486] At step #1836 the video material type VOB_V_KIND is extractedfrom the scenario data St7. If the material is a film type, i.e., amovie converted to television broadcast format (so-called telecineconversion), reverse telecine conversion is set for the video encodemode V_ENCMD, and defined as a video encoding parameter.

[0487] At step #1838 the audio coding method VOB_A_KIND is extractedfrom the scenario data St7, and the encoding method is set as the audioencode method A_ENCMD and set as an audio encoding parameter.

[0488] At step #1840 the initial video encode data V_INTST sets theinitial value of the VBV buffer to a value less than the VBV buffer endvalue set by the last video encode data V_ENDST, and defined as a videoencoding parameter.

[0489] At step #1842 the VOB number VOB_NO of the preceding connectionis set to the preceding VOB number B_VOB_NO based on the setting (=1) ofthe preceding VOB seamless connection flag VOB_Fsb, and set as a systemencode parameter.

[0490] At step #1844 the VOB number VOB_NO of the following connectionis set to the following VOB number F_VOB_NO based on the setting (=1) ofthe following VOB seamless connection flag VOB_Fsf, and set as a systemencode parameter.

[0491] The encoding information table and encode parameters are thusgenerated for a multi-angle VOB Set with non-seamless multi-angleswitching control enabled.

[0492] The process for generating the encode parameters of a seamlessswitching stream with multi-angle control is described below withreference to FIG. 37. This stream is generated when step #1500 in FIG.34 returns YES and the following flags are set as shown: VOB_Fsb 1 orVOB_Fsf=1, VOB_Fp=1, VOB_Fi=1, VOB Fm=1, and VOB_FsV=1.

[0493] The following operation produces the encoding information tablesshown in FIG. 27 and FIG. 28, and the encode parameters shown in FIG.29.

[0494] The following operation produces the encoding information tablesshown in FIG. 27 and FIG. 28, and the encode parameters shown in FIG.29.

[0495] At step #1850, the scenario reproduction sequence (path)contained in the scenario data St7 is extracted, the VOB Set numberVOBS_NO is set, and the VOB number VOB NO is set for one or more VOB inthe VOB Set.

[0496] At step #1852 the maximum bit rate ILV_BR of the interleaved VOBis extracted from the scenario data St7, and the maximum video encodebit rate V_MRATE from the encode parameters is set based on theinterleave flag VOB_Fi setting (=1).

[0497] At step #1854, the minimum interleaved unit presentation timeILVU_MT is extracted from the scenario data St7.

[0498] At step #1856, the video encode GOP structure GOPST values N=15and M=3 are set, and the GOP structure fixing flag GOP_Fxflag is set(=1), based on the multi-scene flag VOB_Fp setting (=1).

[0499] At step #1858, the video encode GOP GOPST is set to “closed GOP”based on the multi-angle seamless switching flag VOB_FsV setting (=1),and the video encoding parameters are thus defined.

[0500] Step #1860 is the common VOB data setting routine, which is asdescribed referring to the flow chart in FIG. 35. Further descriptionthereof is thus omitted here.

[0501] The encode parameters of a seamless switching stream withmulti-angle control are thus defined for a VOB Set with multi-anglecontrol as described above.

[0502] The process for generating the encode parameters for a systemstream in which parental lock control is implemented is described belowwith reference to FIG. 38. This stream is generated when step #1200 inFIG. 34 returns NO and step #1304 returns YES, i.e., the following flagsare set as shown: VOB_Fsb=1 or VOB_Fsf=1, VOB_Fp=1, VOB_Fi=1, VOB_Fm=0.The following operation produces the encoding information tables shownin FIG. 27 and FIG. 28, and the encode parameters shown in FIG. 29.

[0503] At step #1870, the scenario reproduction sequence (path)contained in the scenario data St7 is extracted, the VOB Set numberVOBS_NO is set, and the VOB number VOB_NO is set for one or more VOB inthe VOB Set.

[0504] At step #1872 the maximum bit rate ILV_BR of the interleaved VOBis extracted from the scenario data St7, and the maximum video encodebit rate V_MRATE from the encode parameters is set based on theinterleave flag VOB_Fi setting (=1).

[0505] At step #1872 the number of interleaved VOB divisions ILV_DIV isextracted from the scenario data St7.

[0506] Step #1876 is the common VOB data. setting routine, which is asdescribed referring to the flow chart in FIG. 35. Further descriptionthereof is thus omitted here.

[0507] The encode parameters of a system stream in which parental lockcontrol is implemented are thus defined for a VOB Set with multi-sceneselection control enabled as described above.

[0508] The process for generating the encode parameters for a systemstream containing a single scene is described below with reference toFIG. 70. This stream is generated when step #900 in FIG. 34 returns NO,i.e., when VOB_Fp=0. The following operation produces the encodinginformation tables shown in FIG. 27 and FIG. 28, and the encodeparameters shown in FIG. 29.

[0509] At step #1880, the scenario reproduction sequence (path)contained in the scenario data St7 is extracted, the VOB Set numberVOBS_NO is set, and the VOB number VOB_NO is set for one or more VOB inthe VOB Set.

[0510] At step #1882 the maximum bit rate ILV_BR of the interleaved VOBis extracted from the scenario data St7, and the maximum video encodebit rate V_MRATE from the encode parameters is set based on theinterleave flag VOB_Fi setting (=1).

[0511] Step #1884 is the common VOB data setting routine, which is asdescribed referring to the flow chart in FIG. 35. Further descriptionthereof is thus omitted here.

[0512] These flow charts for defining the encoding information table andencode parameters thus generate the parameters for DVD video, audio, andsystem stream encoding by the DVD formatter.

[0513] Flow Chart: Formatter

[0514] The operation of the subroutine executed by the DVD formattershown as step #2300 in FIG. 34B is described next with reference toFIGS. 49, 59, 51, 52, and 53. This formatter subroutine generates theDVD multimedia bitstream.

[0515] The operation of the DVD encoder ECD 1100 according to thepresent invention is described with reference to the flow chart in FIG.49. Note that those steps shown in FIG. 49 with a double line aresubroutines.

[0516] At step #2310 the program chain information VTS_PGCI is set tothe VTSI management table VTSI_MAT for the number of titles TITLE_NUMbased on the number of titles TITLE_NUM in the VOB Set data stream.

[0517] At step #2312 it is determined whether multi-scene selectioncontrol is enabled based on the multi-scene flag VOB_Fp in the VOB Setdata stream. If step #2312 returns NO, i.e., multi-scene control is notenabled, the procedure moves to step #2114.

[0518] At step #2314 the operation for coding a single scene (VOB)executed by the formatter 1100 of the authoring encoder EC shown in FIG.25 is accomplished. This routine is described later.

[0519] If step #2312 returns YES, i.e., multi-scene control is enabled,the procedure moves to step #2116.

[0520] At step #2316 it is determined whether the information is to beinterleaved or not based on the interleave flag VOB Fi stat-e-in the VOBSet data stream. If step #2316 returns NO, i.e., the information is notto be interleaved, the procedure moves to step #2314. If step #2316returns YES, i.e., the information is to be interleaved, the proceduremoves to step #2318.

[0521] At step #2318 it is determined whether multi-angle control is tobe implemented based on the multi-angle flag VOB_Fm in the VOB Set datastream. If step #2318 returns NO, the parental lock control routine instep #2320 is executed. If step #2318 returns YES, the procedure movesto step #2322.

[0522] At step #2320 the operation for formatting the VOB Set forparental lock control is executed. This subroutine is shown in FIG. 52and described below.

[0523] At step #2322 it is determined whether multi-angle seamlessswitching is required based on the multi-angle seamless switching flagVOB_FsV. If multi-angle switching is accomplished without seamlessswitching, i.e., with non-seamless switching and step #2322 returns NO,the procedure moves to step #2326.

[0524] The multi-angle non-seamless switching control routine executedin step #2326 by the formatter 1100 of the authoring encoder EC in FIG.25 is described later with reference to FIG. 50.

[0525] If multi-angle switching is accomplished with seamless switchingcontrol, i.e., step #2322 returns YES, the procedure moves to step#2324.

[0526] The multi-angle seamless switching control routine executed instep #2324 by the formatter 1100 of the authoring encoder EC in FIG. 25is described later with reference to FIG. 51.

[0527] The cell playback information (PCG information entries C_PBI) ofthe VTS information VTSI set as previously described is then recorded.

[0528] At step #2330 it is determined whether all VOB Sets declared bythe VOB Set number VOBS_NUM have been processed by the formatter. If NO,control loops back to step #2312, and the process runs again. If YES,all sets have been formatted, the procedure terminates.

[0529] Referring to FIG. 50, the multi-angle non-seamless switchingcontrol routine executed in step #2326 when step #2322, FIG. 49, returnsNO is described. This routine defines the interleaved arrangement of themultimedia bitstream MBS, the content of the cell playback information(C_PBI#i) shown in FIG. 16, and the information stored to the navigationpack NV shown in FIG. 20, in the generated DVD multimedia bitstream MBS.

[0530] At step #2340 based on the multi-angle flag VOB Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block mode CBM (FIG. 16) of the cell playbackinformation blocks C_PBI #i containing the VOB control information foreach scene is declared according to the position of the angle data. Forexample, the cell block mode CBM of the MA1 cell (FIG. 23) is declaredas 01b to indicate the beginning of the cell block, the CBM of MA2 isdeclared as 10b to indicate a cell between the first and last cells inthe block, and the CBM of MA3 is declared as 11b to indicate the end ofthe cell block.

[0531] At step #2342 based on the multi-angle flag VOB_Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block type CBT (FIG. 16) of the cell playbackinformation blocks C_PBI #i containing the VOB control information foreach scene is declared as 01b to indicate an “angle.”

[0532] At step #2344 the seamless playback flag SPF (FIG. 16) is set to1 in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

[0533] At step #2346 the STC resetting flag STCDF is set to 1 in thecell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

[0534] At step #2348 the interleaved allocation flag IAF (FIG. 16) isset to 1 in the cell playback information blocks C_PBI #i containing theVOB control information for each scene based on the multi-angle seamlessswitching flag VOB_FsV state, which is set to 1 to indicate interleavingis required.

[0535] At step #2350 the location of the navigation pack NV (relativesector number from the VOB beginning) is detected from the title editingunit (VOB below) obtained from the system encoder 900.in FIG. 25, thenavigation pack NV is detected based on the-minimum interleaved unitpresentation time ILVU_MT information (a formatter parameter obtained instep #1816, FIG. 35), the location of the VOBU expressed as the numberof sectors from the VOB beginning, for example, is thus obtained, andthe title editing unit VOB is divided into interleave units using VOBUunits.

[0536] For example, if in this example the minimum interleaved unitpresentation time ILVU_MT is 2 sec and the presentation time of one VOBUis 0.5 sec., then the VOB is divided into interleave units of 4 VOBUeach. Note that this allocation operation is applied to the VOBconstituting each multi-scene data unit.

[0537] At step #2352 the interleave units of each VOB obtained from step#2350 are arranged in the cell block mode CBM sequence (cell blockbeginning, middle, and end cells) written as the VOB control informationfor each scene in step #2340 to form the interleaved blocks as shown inFIG. 71 or 72. The interleaved blocks are then added to the VTS titleVOBS (VTSTT VOBS). Using the cell block mode CBM declarations above, forexample, the angle data MA1, MA2, and MA3 (FIG. 23) are arranged in thatsequence.

[0538] At step #2354 the relative sector number from the VOBU start iswritten to the VOB end pack address VOBU_EA (FIG. 20) in the navigationpack NV of each VOBU based on the VOBU position information obtained instep #2350.

[0539] At step #2356 the first cell VOEU start address C_FVOBU_SA andthe last cell VOBU start address C_LVOBU_SA expressed as the number ofsectors from the beginning of the VTS title VOBS (VTSTT_VOBS) arewritten as the addresses of the navigation packs NV of the first andlast VOBU in each cell based on the VTS title VOBS (VTSTT VOBS) dataobtained in step #2352.

[0540] The angle #i VOBU start address NSML_AGL_C1_DSTA-NSML_AGL_C9_DSTAof the non-seamless angle information NSML_AGLI (FIG. 20) in thenavigation pack NV of each VOBU is written at step #2358. This addressis expressed as the relative sector number inside the data of theinterleaved blocks formed in step #2352, and declares the addressinformation (FIG. 50) of the navigation pack NV contained in the VOBU ofall angle scenes near the presentation start time of the VOBU beingprocessed.

[0541] At step #2360 “7FFFFFFFh” is written to the angle #i VOBU startaddress NSML_AGL_C1_DSTA-NSML_AGL_C9_DSTA of the non-seamless angleinformation NSML_AGLI (FIG. 20) in the navigation pack NV of each VOBUif the VOBU being processed is the last VOBU of each scene in themulti-scene period.

[0542] This routine thus formats the interleaved blocks for multi-anglenon-seamless switching control in the multi-scene period, and formatsthe cell control information as the reproduction control information forthose multiple scenes.

[0543] Referring to FIG. 51, the multi-angle seamless switching controlroutine executed in step #2324 when step #2322, FIG. 49, returns YES isdescribed. This routine defines the interleaved arrangement of themultimedia bitstream MBS, the content of the cell playback information(C_PBI#i) shown in FIG. 16, and the information stored to the navigationpack NV shown in FIG. 20, in the generated DVD multimedia bitstream MBS.

[0544] At step #2370 based on the multi-angle flag VOB_Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block mode CBM (FIG. 16) of the cell playbackinformation blocks C_PBI #i containing the VOB control information foreach scene is declared according to the position of the angle data. Forexample, the cell block mode CBM of the MA1 cell (FIG. 23) is declaredas 01b to indicate the beginning of the cell block, the CBM of MA2 isdeclared as 10b to indicate a cell between the first and last cells inthe block, and the CBM of MA3 is declared as 11b to indicate the end ofthe cell block.

[0545] At step #2372 based on the multi-angle flag VOB_Pm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block type CBT (FIG. 16) of the cell playbackinformation blocks C_PBI #I containing the VOB control information foreach scene is declared as 01b to indicate an “angle.”

[0546] At step #2374 the seamless playback flag SPF (FIG. 16) is set to1 in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB Fsb state, which is set to 1 to indicate a seamlessconnection.

[0547] At step #2376 the-STC resetting flag STCDF is set to 1 in thecell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

[0548] At step #2378 the interleaved allocation flag IAF (FIG. 16) isset to 1 in the cell playback information blocks C_PBI #i containing theVOB control information for each scene based on the multi-angle seamlessswitching flag VOB_FsV state, which is set to 1 to indicate interleavingis required.

[0549] At step #2380 the location of the navigation pack NV (relativesector number from the VOB beginning) is detected from the title editingunit (VOB below) obtained from the system encoder 900 in FIG. 25, thenavigation pack NV is detected based on the minimum interleaved unitpresentation time ILVU_MT information (a formatter parameter obtained instep #1854, FIG. 37), the location of the VOBU expressed as the numberof sectors from the VOB beginning, for example, is thus obtained, andthe title editing unit VOB is divided into interleave units using VOBUunits.

[0550] For example, if in this example the minimum interleaved unitpresentation time ILVU_MT is 2 sec and the presentation time of one VOBUis 0.5 sec., then the VOB is divided into interleave units of 4 VOBUeach. Note that this allocation operation is applied to the VOBconstituting each multi-scene data unit.

[0551] At step #2382 the-interleave units.of each VOB obtained from step#2380 are arranged in the cell block mode CBM sequence (cell blockbeginning, middle, and end cells) written as the VOB control informationfor each scene in step #2360 to form the interleaved blocks as shown inFIG. 71 or 72. The interleaved blocks are then added to the VTS titleVOBS (VTSTT_VOBS). Using the cell block mode CBM declarations above, forexample, the angle data MA1, MA2, and MA3 (FIG. 23) are arranged in thatsequence.

[0552] At step #2384 the relative sector number from the VOBU start iswritten to the VOB end pack address VOBU_EA (FIG. 20) in the navigationpack NV of each VOBU based on the VOBU position information obtained instep #2360.

[0553] At step #2386 the first cell VOBU start address C_FVOBU_SA andthe last cell VOBU start address C_LVOBU_SA expressed as the number ofsectors from the beginning of the VTS title VOBS (VTSTT_VOBS) arewritten as the addresses of the navigation packs NV of the first andlast VOBU in each cell based on the VTS title VOBS (VTSTT_VOBS) dataobtained in step #2382.

[0554] At step #2388 the relative sector number from the VOBU start iswritten to the VOB end pack address VOBU_EA (FIG. 20) in the navigationpack NV of each VOBU based on the interleave unit data obtained in step#2370.

[0555] The angle #i VOBU start address SML_AGL_C1_DSTA-SML_AGL_C9_DSTAof the seamless angle information SML_AGLI (FIG. 20) in the navigationpack NV of each VOBU is written at step #2390. This address is expressedas the relative sector number inside the data of the interleaved blocksformed in step #2382, and declares the address information of thenavigation pack NV contained in the VOBU of all angle scenes with astart time contiguous to the reproduction end time of the VOBU beingprocessed.

[0556] At step #2392 “7FFFFFFFh” is written to the angle #i VOBU startaddress SML_AGL_C1_DSTA-SML_AGL_C9_DSTA of the seamless angleinformation SML_AGLI (FIG. 20) in the navigation pack NV of the VOBUcontained in the interleaved unit if the interleave unit arranged instep #2382 is the last interleave unit of each scene in the multi-sceneperiod.

[0557] This routine thus formats the interleaved blocks for multi-angleseamless switching control in the multiscene period, and formats thecell control information as the reproduction control information forthose multiple scenes.

[0558] The parental lock subroutine (step #2320, FIG. 49) executed whenstep #2318 in FIG. 49 returns NO, i.e.; when it is determined thatparental lock control is implemented and not multi-angle control, isdescribed next with reference to FIG. 52.

[0559] The parental lock subroutine described below writes theinterleave unit arrangement of the multimedia bitstream, the content ofthe PGC information entries C_PBI #i (cell playback information) shownin FIG. 16, and the navigation pack NV information shown in FIG. 20, tothe generated DVD multimedia bitstream.

[0560] At step #2402 a value “00b” is written to the cell block mode CBM(FIG. 16) of the cell playback information blocks C PBI #i containingthe VOB control information for each scene based on the multi-angle flagVOB_Fm state, which is set to 0 to indicate that multi-angle control isnot enabled in the multi-scene period.

[0561] At step #2404 the seamless playback flag SPF (FIG. 16) is set to1 in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

[0562] At step #2406 the STC resetting flag STCDF is set to 1 in thecell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

[0563] At step #2408 the interleaved allocation flag IAF (FIG. 16) isset to 1 in the cell playback information blocks C_PBI #i containing theVOB control information for each scene based on the multi-angle seamlessswitching flag VOB_FSV state, which is set to 1 to indicate interleavingis required.

[0564] At step #2410 the navigation pack NV position information (therelative sector number from the VOB start) is detected from the titleediting unit (VOB) obtained from the system encoder 900 (FIG. 25). Thenavigation pack NV is then detected based on the number of interleavedVOB divisions ILV_DIV, a formatter parameter obtained in step #1874 inFIG. 38, to obtain the VOBU position information (number of sectors fromthe VOB start), and divide each VOB into the specified number ofinterleave units in VOBU units.

[0565] At step #2412 the interleave units obtained in step #2410 arethen interleaved. For example, the interleave units are arranged inascending VOB number sequence to create the interleaved blocks as shownin FIG. 71 or 72, and the interleaved blocks are added to the VTS titleVOBS (VTSTT_VOBS).

[0566] At step #2414 the relative sector number from the VOBU start iswritten to the VOB end pack address VOBU_EA (FIG. 20) in the navigationpack NV of each VOBU based on the VOBU position information obtained instep #2186.

[0567] At step #2416 the first cell VOBU start address C_FVOBU_SA andthe last cell VOBU start address C_LVOBU_SA expressed as the number ofsectors from the beginning of the VTS title VOBS (VTSTT_VOBS) arewritten as the addresses of the navigation packs NV of the first andlast VOBU in each cell based on the VTS title VOBS (VTSTT_VOBS) dataobtained in step #2412.

[0568] At step #2418 the relative sector number to the last interleaveunit pack is written to the ILVU end pack address ILVU_EA in thenavigation pack NV of the VOBU forming the interleaved units based onthe interleaved unit data obtained from step #2412.

[0569] At step #2420, the relative sector number in the interleavedblock data formed in step #2412 is written to the next-ILVU startaddress NT_ILVU_SA as the position information of the next ILVU in thenavigation packs NV of the VOBU contained in the interleaved unit ILVU.

[0570] At step #2422 the interleaved unit flag ILVU flag is set to 1 inthe navigation packs NV of the VOBU contained in the interleaved unitILVU.

[0571] At step #2424, the Unit END flag of the navigation pack NV in thelast VOBU of the interleaved unit ILVU is set to 1.

[0572] At step #2426 “FFFFFFFFh” is written to the nextILVU startaddress NT_ILVU_SA of the navigation pack NV of the VOBU in the lastinterleaved unit ILVU of each VOB.

[0573] The operation described above thus formats the interleaved blocksto enable parental lock control in the multi-scene periods, and formatsthe control information in the cells, i.e., the cell playback controlinformation for the multi-scene periods.

[0574] The single scene subroutine executed as step #2314 in FIG. 49when steps #2312 or #2316 return NO, i.e., when the scene is determinedto be a single scene and not a multi-scene period, is described nextusing FIG. 53.

[0575] The single scene subroutine described below writes the interleaveunit arrangement of the multimedia bitstream, the content of the PGCinformation entries C_PBI #i (cell playback information) shown in FIG.16, and the navigation pack NV information shown in FIG. 20, to thegenerated DVD multimedia bitstream.

[0576] At step #2430 a value “00b” indicating a “non-cell block”, i.e.,that there is only one cell in the functional block, is written to thecell block mode CBM (FIG. 16) of the cell playback information blocksC_PBI #i containing the VOB control information for each scene based onthe multi-scene flag VOB_Fp state, which is set to 0 to indicate thatthe scene is a single scene and not part of a multi-scene period.

[0577] At step #2432 the interleaved allocation flag IAF (FIG. 16) isset to 0 in the cell playback information blocks C_PBI #i containing theVOB control information for each scene based on the multi-angle seamlessswitching flag VOB_FsV state, which is set to 0 to indicate interleavingis not required.

[0578] At step #2434 the navigation pack NV position information (therelative sector number from the VOB start) is detected from the titleediting unit (VOB) obtained from the system encoder 900 (FIG. 25),placed in the VOBU unit, and added to the VTS title VOBS (VTSTT_VOBS),the video and other stream data of the multimedia bitstream.

[0579] At step #2436 the relative sector number from the VOBU start iswritten to the VOB end pack address VOBU_EA (FIG. 20) in the navigationpack NV of each VOBU based on the VOBU position information obtained instep #2434.

[0580] At step #2438 the first cell VOBU start address C_FVOBU_SA andthe last cell VOBU start address C_LVOBU_SA expressed as the number ofsectors from the beginning of and the end of, respectively, the VTStitle VOBS (VTSTT_VOBS) of the value written as the addresses of thenavigation packs NV of the first and last VOBU in cell based on the VTStitle VOBS (VTSTT_VOBS) data obtained in step #2434.

[0581] At step #2440 the state determined as a result of step #300 or#600 in FIG. 34, i.e., whether preceding VOB seamless connection flagVOB_Fsb is set to 1 indicating a seamless connection to the preceding orfollowing scenes, is evaluated. If step #2440 returns YES, the proceduremoves to step #2442.

[0582] At step #2442 the seamless playback flag SPF (FIG. 16) is set to1 in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

[0583] At step #2444 the STC resetting flag STCDF is set to 1 in thecell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1.

[0584] If step #2440 returns NO, i.e., there is not a seamlessconnection to the preceding scene, the procedure moves to step #2446.

[0585] At step #2446 the seamless playback flag SPF (FIG. 16) is set to0 in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 0 to indicate anon-seamless connection.

[0586] At step #2448 the STC resetting flag STCDF is set to 0 in thecell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 0.

[0587] The operation described above thus formats a multimedia bitstreamfor a single scene period, and records the control information in thecells, i.e., the cell playback control information (C_PBI #i, FIG. 16),and the information in the navigation pack NV (FIG. 20), to the producedDVD multimedia bitstream.

[0588] Decoder Flow Charts

[0589] A. Disk-to-stream Buffer Transfer Flow:

[0590] The decoding information table produced by the decoding systemcontroller 2300 based on the scenario selection data St51 is describedbelow referring to FIGS. 54 and 55. The decoding information tablecomprises the decoding system table shown in FIG. 54, and the decodingtable shown in FIG. 55.

[0591] As shown in FIG. 54, the decoding system table comprises ascenario information register and a cell information register. Thescenario information register records the title number and otherscenario reproduction information selected by the user and extractedfrom the scenario selection data St51. The cell information registerextracts and records the information required to reproduce the cellsconstituting the program chain PGC based on the user-defined scenarioinformation extracted into the scenario information register.

[0592] More specifically, the scenario information register containsplural sub-registers, i.e., the angle number ANGLE_NO_reg, VTS numberVTS_NO_reg, PGC number VTS_PGCI_NO reg, audio ID AUDIO_ID_reg,sub-picture ID SP_ID_reg, and the system clock reference SCR bufferSCR_buffer.

[0593] The angle number ANGLE_NO_reg stores which angle is reproducedwhen there are multiple angles in the reproduction program chain PGC.

[0594] The VTS number VTS_NO_reg records the number of the next VTSreproduced from among the plural VTS on the disk.

[0595] The PGC number VTS_PGCI_NO_reg records which of the pluralprogram chains PGC present in the video title set VTS is to bereproduced for parental lock control or other applications.

[0596] The audio ID AUDIO_ID_reg records which of the plural audiostreams in the VTS are to be reproduced.

[0597] The sub-picture ID SP_ID_reg records which of the pluralsub-picture streams is to be reproduced when there are pluralsub-picture streams in the VTS.

[0598] The system clock reference SCR buffer SCR_buffer is the bufferfor temporarily storing the system clock reference SCR recorded to thepack header as shown in FIG. 19. As described using FIG. 26, thistemporarily stored system clock reference SCR is output to the decodingsystem controller 2300 as the bitstream control data St63.

[0599] The cell information register contains the followingsub-registers: the cell block mode CBM_reg, cell block type CBT_reg,seamless reproduction flag SPF_reg, interleaved allocation flag IAF_reg,STC resetting flag STCDF, seamless angle change flag SACF_reg, firstcell VOBU start address C_FVOBU_SA_reg, and last cell VOBU start addressC_LVOBU_SA_reg.

[0600] The cell block mode CBM_reg stores a value indicating whetherplural cells constitute one functional block. If there are not pluralcells in one functional block, CBM_reg stores N_BLOCK. If plural cellsconstitute one functional block, the value F_CELL is stored as theCBM_reg value of the first cell in the block, L_CELL is stored as theCBM_reg value of the last cell in the block, and BLOCK is stored as theCBM_reg of value all cells between the first and last cells in theblock.

[0601] The cell block type CBT_reg stores a value defining the type ofthe block indicated by the cell block mode CBM_reg. If the cell block isa multi-angle block, A_BLOCK is stored; if not, N_BLOCK is stored.

[0602] The seamless reproduction flag SPF_reg stores a value definingwhether that cell is seamless connected with the cell or cell blockreproduced therebefore. If a seamless connection is specified, SML isstored; if a seamless connection is not specified, NSML is stored.

[0603] The interleaved allocation flag IAF_reg stores a valueidentifying whether the cell exists in a contiguous or interleavedblock. If the cell is part of a an interleaved block, ILVB is stored;otherwise.N_ILVB is stored.

[0604] The STC resetting flag STCDF defines whether the system timeclock STC used for synchronization must be reset when the cell isreproduced; when resetting the system time clock STC is necessary,STC_RESET is stored; if resetting is not necessary, STC_NRESET isstored.

[0605] The seamless angle change flag SACF_reg stores a value indicatingwhether a cell in a multi-angle period should be connected seamlessly atan angle change. If the angle change is seamless, the seamless anglechange flag SACF is set to SML; otherwise it is set to NSML.

[0606] The first cell VOBU start address C_FVOBU_SA_reg stores the VOBUstart address of the first cell in a block. The value of this address isexpressed as the distance from the logic sector of the first cell in theVTS title VOBS (VTSTT_VOBS) as measured by and expressed (stored) as thenumber of sectors.

[0607] The last cell VOBU start address C_LVOBU_SA reg stores the VOBUstart address of the last cell in the block. The value of this addressis also expressed as the distance from the logic sector of the firstcell in the VTS title VOBS (VTSTT_VOBS) measured by and expressed(stored) as the number of sectors.

[0608] The decoding table shown in FIG. 55 is described below. As shownin FIG. 55, the decoding table comprises the following registers:information registers for non-seamless multi-angle control, informationregisters for seamless multi-angle control, a VOBU information register,and information registers for seamless reproduction.

[0609] The information registers for non-seamless multi-angle controlcomprise sub-registers NSML_AGL_C1_DSTA_reg-NSML_(AGL_C)9_DSTA_reg.

[0610] NSML_AGL_C1_DSTAreg-NSML_AGL_C9_DSTA_reg record theNMSL_AGL_C1_DSTA-NMSL_AGL_C9_DSTA values in the PCI packet shown in FIG.20.

[0611] The information registers for seamless multi-angle controlcomprise sub-registers SML_AGL_C1_DSTA_reg-SML_AGL_C9_DSTA_reg.

[0612] SML_AGL_C1_DSTA_reg-SML_AGL_C9_DSTA_reg record theSML_AGL_C1_DSTA-SML_AGL_C9_DSTA values in the DSI packet shown in FIG.20.

[0613] The VOBU information register stores the end pack address VOBU_EAin the DSI packet shown in FIG. 20.

[0614] The information registers for seamless reproduction comprise thefollowing sub-registers: an interleaved unit flag ILVU_flag_reg, UnitEND flag UNIT_END_flag_reg, Interleaved Unit End Address ILVU_EA_reg,Next Interleaved Unit Start Address NT_ILVU_SA_reg, the presentationstart time of the first video frame in the VOB (Initial Video FramePresentation Start Time) VOB_V_SPTM_reg, the presentation end time ofthe last video frame in the VOB (Final Video Frame PresentationTermination Time) VOB_V_EPTM_reg, audio reproduction stopping time 1 VOBA STP_PTM1_reg, audio reproduction stopping time 2 VOB_A_STP_PTM2_reg,audio reproduction stopping period 1 VOB_A_GAP_LEN1_reg, and audioreproduction stopping period 2 VOB_A_GAP_LEN2_reg.

[0615] The interleaved unit flag ILVU flag reg stores the valueindicating whether the video object unit VOBU is in an interleavedblock, and stores ILVU if it is, and N_ILVU if not.

[0616] The Unit END flag UNIT_END_flag_reg stores the value indicatingwhether the video object unit VOBU is the last VOBU in the interleavedunit ILVU. Because the interleaved unit ILVU is the data unit forcontinuous reading, the UNIT_END_flag_reg stores END if the VOBUcurrently being read is the last VOBU in the interleaved unit ILVU, andotherwise stores N_END.

[0617] The Interleaved Unit End Address ILVU_EA_reg stores the addressof the last pack in the ILVU to which the VOBU belongs if the VOBU is inan interleaved block. This address is expressed as the number of sectorsfrom the navigation pack NV of that VOBU.

[0618] The Next Interleaved Unit Start Address NT_ILVU_SA reg stores thestart address of the next interleaved unit ILVU if the VOBU is in aninterleaved block. This address is also expressed as the number ofsectors from the navigation pack NV of that VOBU.

[0619] The Initial Video Frame Presentation Start Time registerVOB_V_SPTM_reg stores the time at which presentation of the first videoframe in the VOB starts.

[0620] The Final Video Frame Presentation Termination Time registerVOB_V_EPTM_reg stores the time at which presentation of the last videoframe in the VOB ends.

[0621] The audio reproduction stopping time 1 VOB_A_STP_PTM1_reg storesthe time at which the audio is to be paused to enableresynch-ronization, and the audio reproduction stopping period 1VOB_A_GAP_LEN1_reg stores the length of this pause period.

[0622] The audio reproduction stopping time 2 VOB_A STP_PTM2_reg andaudio reproduction stopping period 2 VOB_A_GAP_LEN2_reg store the samevalues.

[0623] The operation of the DVD decoder DCD according to the presentinvention as shown in FIG. 26 is described next below with reference tothe flow chart in FIG. 56.

[0624] At step #310202 it is first determined whether a disk has beeninserted. If it has, the procedure moves to step #310204.

[0625] At step #310204, the volume file structure VFS (FIG. 21) is read,and the procedure moves to step #310206.

[0626] At step #310206, the video manager VMG (FIG. 21) is read and thevideo title set VTS to be reproduced is extracted. The procedure thenmoves to step #310208.

[0627] At step #310208, the video title set menu address informationVTSM_C_ADT is extracted from the VTS information VTSI, and the proceduremoves to step #310210.

[0628] At step #310210 the video title set menu VTSM_VOBS is read fromthe disk based on the video title set menu address informationVTSM_C_ADT, and the title selection menu is presented.

[0629] The user is thus able to select the desired title from this menuin step #310212. If the titles include both contiguous titles with nouser-selectable content, and titles containing audio numbers,sub-picture numbers, or multi-angle scene content, the user must alsoenter the desired angle number. Once the user selection is completed,the procedure moves to step #310214.

[0630] At step #310214, the VTS_PGCI #i program chain (PGC) data blockcorresponding to the title number selected by the user is extracted fromthe VTSPGC information table VTS_PGCIT, and the procedure moves to step#310216.

[0631] Reproduction of the program chain PGC then begins at step#310216. When program chain PGC reproduction is finished, the decodingprocess ends. If a separate title is thereafter to be reproduced asdetermined by monitoring key entry to the scenario selector, the titlemenu is presented again (step #310210).

[0632] Program chain reproduction in step #310216 above is described infurther detail below referring to FIG. 57. The program chain PGCreproduction routine consists of steps #31030, #31032, #31034, and#31035 as shown.

[0633] At step #31030 the decoding system table shown in FIG. 54 isdefined. The angle number ANGLE_NO_reg, VTS number VTS_NO_reg, PGCnumber VTS_PGCI_NO_reg, audio ID AUDIO_ID_reg, and sub-picture IDSP_ID_reg are set according to the selections made by the user using thescenario selector 2100.

[0634] Once the PGC to be reproduced is determined, the correspondingcell information (PGC information entries C_PBI #j) is extracted and thecell information register is defined. The sub-registers therein that aredefined are the cell block mode CBM_reg, cell block type CBT_reg,seamless reproduction flag SPF_reg, interleaved allocation flag IAF_reg,STC resetting-.flag STCDF, seamless angle change flag SACF_reg, firstcell VOBU start address C_FVOBU_SA_reg, and last cell VOBU start addressC_LVOBU_SA_reg.

[0635] Once the decoding system table is defined, the processtransferring data to the stream buffer (step #31032) and the processdecoding the data in the stream buffer (step #31034) are activated inparallel.

[0636] The process transferring data to the stream buffer (step #31032)is the process of transferring data from the recording medium M to thestream buffer 2400. This is, therefore, the processing of reading therequired data from the recording medium M and inputting the data to thestream buffer 2400 according to the user-selected title information andthe playback control information (navigation packs NV) written in thestream.

[0637] The routine shown as step #31034 is the process for decoding thedata stored to the stream buffer 2400 (FIG. 26), and outputting thedecoded data to the video data output terminal 3600 and audio dataoutput terminal 3700. Thus, is the process for decoding and reproducingthe data stored to the stream buffer 2400.

[0638] Note that step #31032 and step #31034 are executed in parallel.

[0639] The processing unit of step #31032 is the cell, and as processingone cell is completed, it is determined in step #31035 whether thecomplete program chain PGC has been processed. If processing thecomplete program chain PGC is not completed, the decoding system tableis defined for the next cell in step #31030. This loop from step #31030through step #31035 is repeated until the entire program chain PGC isprocessed.

[0640] The stream buffer data transfer process of step #31032 isdescribed in further detail below referring to FIG. 70. The streambuffer data transfer process (step #31032) comprises steps #31040,#31042, #31044, #31046, and #31048 shown in the figure.

[0641] At step #31040 it is determined whether the cell is a multi-anglecell. If not, the procedure moves to step #30144.

[0642] At step #31044 the non-multi-angle cell decoding process isexecuted.

[0643] However, if step #30140 returns YES because the cell is amulti-angle cell, the procedure moves to step #30142 where the seamlessangle change flag SACF is evaluated to determine whether seamless anglereproduction is specified.

[0644] If seamless angle reproduction is specified, the seamlessmulti-angle decoding process is executed in step #30146. If seamlessangle reproduction is not specified, the non-seamless multi-angledecoding process is executed in step #30148.

[0645] The non-multi-angle cell decoding process (step #31044, FIG. 62)is described further below with reference to FIG. 63. Note that thenon-multi-angle cell decoding process (step #31044) comprises the steps#31050, #31052, and #31054.

[0646] The first step #31050 evaluates the interleaved allocation flagIAF_reg to determine whether the cell is in an interleaved block. If itis, the non-multi-angle interleaved block process is executed in step#31052.

[0647] The non-multi-angle interleaved block process (step #31052)processes scene branching and connection where seamless connections arespecified in, for example, a multi-scene period.

[0648] However, if the cell is not in an interleaved block, thenon-multi-angle contiguous block process is executed in step #31054.Note that the step #31054 process is the process executed when there isno scene branching or connection.

[0649] The non-multi-angle interleaved block process (step #31052, FIG.63) is described further below with reference to FIG. 64.

[0650] At step #31060 the reading head 2006 is jumped to the first cellVOBU start address C_FVOBU_SA read from the C_FVOBU_SA_reg register.

[0651] More specifically, the address data C_FVOBU_SA_reg stored in thedecoding system controller 2300 (FIG. 26) is input as bitstreamreproduction control signal St53 to the reproduction controller 2002.The reproduction controller 2002 thus controls the recording media driveunit 2004 and signal processor 2008 to move the reading head 2006 to thespecified address, data is read, error correction code ECC and othersignal processing is accomplished by the signal processor 2008, and thecell start VOBU data is output as the reproduced bitstream St61 to thestream buffer 2400. The procedure then moves to step #31062.

[0652] At step #31062 the DSI packet data in the navigation pack NV(FIG. 20) is extracted in the stream buffer 2400, the decoding table isdefined, and the procedure moves to step #31064. The registers set inthe decoding table are the ILVU_EA_reg, NT_ILVU_SA_reg, VOB_V_SPTM_reg,VOB_V_EPTM_reg, VOB_A_STP_PTM1_reg, VOB_A_STP_PTM2_reg,VOB_A_GAP_LEN1_reg, and VOB_A_GAP_LEN2_reg.

[0653] At step #31064 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the ILVU end pack address ILVU_EA_reg, i.e., the datafor one interleaved unit ILVU, is transferred to the stream buffer 2400.The procedure then moves to step #31066.

[0654] More specifically, the address data ILVU_EA_reg stored in thedecoding system controller 2300 (FIG. 26) is supplied to thereproduction controller 2002. The reproduction controller 2002 thuscontrols the recording media drive unit 2004 and signal processor 2008to read the data to the ILVU_EA_reg address, and after error correctioncode ECC and other signal processing is accomplished by the signalprocessor 2008, the data for the first ILVU in the cell is output as thereproduced bitstream St61 to the stream buffer 2400. It is thus possibleto output the data for one contiguous interleaved unit ILVU on therecording medium M to the stream buffer 2400.

[0655] At step #31066 it is determined whether all interleaved units inthe. interleaved block have been read and transferred. If theinterleaved unit ILVU processed is the last ILVU in the interleavedblock, “0x7FFFFFFF” indicating termination is set to the next-ILVU startaddress NT_ILVU_SA_reg as the next read address. If all interleavedunits in the interleaved block have thus been processed, the proceduremoves to step #31068.

[0656] At step #31068 the reading head 2006 is again jumped to theaddress NT_ILVU_SA_reg of the next interleave unit to be reproduced, andthe procedure loops back to step #31062. Note that this jump is alsoaccomplished as described above, and the loop from step #31062 to step#31068 is repeated.

[0657] However, if step #31066 returns YES, i.e., all interleaved unitILVU in the interleaved block have been transferred, step #31052terminates.

[0658] The non-multi-angle interleaved block process (step #31052) thustransfers the data of one cell to the stream buffer 2400.

[0659] The non-multi-angle contiguous block process is executed in step#31054, FIG. 63, is described further below with reference to FIG. 65.

[0660] At step #31070 the reading head 2006 is jumped to the first cellVOBU start address C_FVOBU_SA read from the C_FVOBU_SA_reg register.This jump is also accomplished as described above, and the loop fromstep #31072 to step #31076 is initiated.

[0661] At step #31072 the DSI packet data in the navigation pack NV(FIG. 20) is extracted in the stream buffer 2400, the decoding table isdefined and the procedure moves to step #31074. The registers set in thedecoding table are the VOBU_EA_reg, VOB_V_SPTM_reg, VOB_V_EPTM_reg,VOB_A_STP_PTMl_reg, VOB_A_STP_PTM2_reg, VOB_A_GAP_LEN1_reg, andVOB_A_GAP_LEN2_reg.

[0662] At step #31074 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the end pack address VOBU_EA_reg, i.e., the data forone video object unit VOBU, is transferred to the stream buffer 2400.The procedure then moves to step #31076. The data for one video objectunit VOBU contiguously arrayed to the recording medium M can thus betransferred to the stream buffer 2400.

[0663] At step #31076 it is determined whether all cell data has beentransferred. If all VOBU in the cell has not been transferred, the datafor the next VOBU is read continuously, and the process loops back tostep #31070.

[0664] However, if all VOBU data in the cell has been transferred asdetermined by the C_LVOBU_SA_reg value in step #31076, thenon-multi-angle contiguous block process (step #31054) terminates. Thisprocess thus transfers the data of one cell to the stream buffer 2400.

[0665] Another method of accomplishing the non-multiangle cell decodingprocess (step #31044, FIG. 62) is described below with reference to FIG.64.

[0666] At step #31080 the reading head 2006 is jumped to the first cellVOBU start address C_FVOBU_SA_reg, and the first VOBU data in the cellis transferred to the stream buffer 2400. The procedure then moves tostep #31081.

[0667] At step #31081 the DSI packet data in the navigation pack NV(FIG. 20) is extracted in.the stream buffer 2400, the decoding table isdefined, and the procedure moves to step #31082. The registers set inthe decoding table are the SCR_buffer, VOBU_EA_reg, ILVU_flag_reg,UNIT_END_flag_reg, ILVU_EA_reg, NT_ILVU_SA_reg, VOB_V_SPTM_reg,VOB_V_EPTM_reg, VOB_A_STP_PTM1_reg, VOB_A STP PTM2_reg,VOB_A_GAP_LEN1_reg, and VOB_A_GAP_LEN2_reg.

[0668] At step #31082 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the end pack address VOBU_EA_reg, i.e., the data forone video object unit VOBU, is transferred to the stream buffer 2400.The procedure then moves to step #31083.

[0669] At step #31083 is determined whether all cell VOBU data has beentransferred. If it has, the process (step #31044) terminates. If it hasnot, the procedure moves to step #31084.

[0670] At step #31084 it is determined whether the VOBU is the last VOBUin the interleaved unit. If not, the process loops back to step #31081.If so, the procedure advances to step #31085. It is thus possible totransfer one cell of data in VOBU units to the stream buffer 2400.

[0671] The loop from step #31081 to step #31084 repeats as describedabove.

[0672] At step #31085 it is determined whether the interleaved unit ILVUis the last in the interleaved block. If so, step #31044 terminates. Ifnot, the procedure advances to step #31086.

[0673] At step #31086 the reading head 2006 is jumped to the addressNT_ILVU_SA reg of the next interleave unit, and the procedure loops backto step #31081. It is thus possible to transfer the data for one cell tothe stream buffer 2400.

[0674] The seamless multi-angle decoding process executed in step#31046, FIG. 62, is described below referring to FIG. 67.

[0675] At step #31090 the reading head 2006 is jumped to the first cellVOBU start address C_FVOBU_SA read from the C_FVOBU_SA_reg register, andthe first VOBU data in the cell is transferred to the stream buffer2400. The procedure then moves to step #31091. This jump is alsoaccomplished as described above, and the loop from step #31091 to step#31095 is initiated.

[0676] At step #31091 the DSI packet data in the navigation pack NV(FIG. 20) is extracted in the stream buffer 2400, the decoding table isdefined, and the procedure moves to step #31092. The registers set inthe decoding table are the ILVU_EA_reg, SML_AGL_C1_DSTA_regSML_AGL_C9_DSTA_reg, VOB_V_SPTM_reg, VOB_V_EPTM_reg, VOB_A_STP_PTMl_reg,VOB_A_STP_PTM2_reg, VOB_A_GAP_LEN1_reg, and VOB_A_GAP_LEN2_reg.

[0677] At step #31092 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the ILVU end pack address ILVU_EA_reg, i.e., the datafor one ILVU, is transferred to the stream buffer 2400. The procedurethen moves to step #31093. It is thus possible to output the data forone contiguous interleaved unit ILVU on the recording medium M to thestream buffer 2400.

[0678] At step #31093 the ANGLE_NO_reg is updated, and the proceduremoves to step #31094. This update operation resets the ANGLE_NO_reg tothe angle number of the angle selected by the user when the user changesthe angle using the scenario selector 2100 (FIG. 26).

[0679] At step #31094 it is determined whether the angle cell data hasall been transferred. If all ILVU in the cell have not been transferred,the procedure moves to step #31095. If all ILVU in the cell have beentransferred, the process terminates.

[0680] At step #31095 the reading head 2006 is jumped to the next angle(SML_AGL_C#n_reg), and the process loops back to step #31091. Note thatSML_AGL_C#n_reg is the address of the angle to which the ANGLE NO regwas updated in step #31093.

[0681] It is thus possible to transfer the data for the angle selectedby the user to the stream buffer 2400 in ILVU units.

[0682] The non-seamless multi-angle decoding process is executed in step#30148, FIG. 62, is described below referring to FIG. 68.

[0683] At step #31100 the reading head 2006 is jumped to the first cellVOBU start address C_FVOBU_SA read from the C_FVOBU_SA reg register, andthe first VOBU data in the cell is transferred to the stream buffer2400. The procedure then moves to step #31101. This jump is alsoaccomplished as described above, and the.loop from step #31101 to step#31106 is initiated.

[0684] At step #31101 the DSI packet data in the navigation pack NV(FIG. 20) is extracted in the stream buffer 2400, the decoding table isdefined, and the procedure moves to step #31102. The registers set inthe decoding table are the VOBU_EA_reg, NSML_AGL_C1_DSTA_reg,NSML_AGL_C9_DSTA_reg, VOB_V_SPTM_reg, VOB_V_EPTM_reg,VOB_A_STP_PTMl_reg, VOB_A_STP_PTM2_reg, VOB_A_GAP_LEN1_reg, andVOB_A_GAP_LEN2_reg.

[0685] At step #31102 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the end pack address VOBU_EA reg, i.e., the data forone VOBU, is transferred to the stream buffer 2400. The procedure thenmoves to step #31103. It is thus possible to output the data for onecontiguous video object unit VOBU on the recording medium M to thestream buffer 2400.

[0686] At step #31103 the ANGLE_NO_reg is updated, and the proceduremoves to step #31104. This update operation resets the ANGLE_NO_reg tothe angle number of the angle selected by the user when the user changesthe angle using the scenario selector 2100 (FIG. 26).

[0687] At step #31104 it is determined whether the angle cell data hasall been transferred. If all VOBU in the cell have not been transferred,the procedure moves to step #31105. If all VOBU in the cell have beentransferred, the process terminates.

[0688] At step #31105.the reading head 2006 is jumped to the next angle(NSML_AGL_C#n_reg), and the process advances to step #31106. Note thatNSML_AGL_C#n_reg is the address of the angle to which the ANGLE_NO_regwas updated in step #31103.

[0689] It is thus possible to transfer the data for the angle selectedby the user to the stream buffer 2400 in VOBU units.

[0690] Step #31106 is an effective step for high speed angle switching,and simply clears the stream buffer 2400. By thus clearing the streambuffer 2400 the data for the newly selected angle can be reproducedwithout reproducing the angle data that is still not decoded. In otherwords, clearing the stream buffer 2400 enables faster response to useroperations.

[0691] It is very important that DVD decoder according to the presentinvention can promptly moves to the next data reading process andeffectively performs the data reading once after the detection of theend of data such as interleave unit ILVU and video object unit VOBU forthe sake of seamless reproduction which is one of main targets of thepresent invention.

[0692] With reference to FIG. 69, a construction of the stream buffer2400 which can performs the end detection of interleave unit ILVU isdescribed briefly. The stream buffer 2400 comprises a VOB buffer 2402, asystem buffer 2404, a navigation pack extractor 2406, and a data counter2408. The system buffer 2404 temporarily stores the title control dataVTSI(FIG. 16) included in signal St61, and outputs a control informationSt2450 (St63) such as VTS_PGC.

[0693] The VOB buffer 2402 temporarily stores the title VOB dataVTSTT_VOB (FIG. 16), and the stream St67 to the system decoder 2500.

[0694] The NV (navigation pack) extractor 2406 receives the VOB data atthe same time with the VOB buffer 2402, and extracts the navigation packNV therefrom. The NV extractor 2406 furthermore extracts the VOBU finalpack address COBU_EA or ILVU final pack address ILVU_EA which are theDSI generation information DSI_GI shown in FIG. 19 to produce a packaddress information St2452 (St63).

[0695] The data counter 2408 receives the VOB data at the same time withthe VOB buffer 2402, and counts each of pack data shown in FIG. 19 byteby byte. Then, the data counter 2408 produces a pack input terminatingsignal St2454 (St63) at the time when the inputting of pack data iscompleted.

[0696] Due to its construction shown in FIG. 69, the stream buffer 2400performs the VOBU data transfer as examples at step #31064 of FIG. 64,as follows. The stream buffer 2400 outputs the VOBU data for the NVextractor 2406 and data counter 2408 at the same time when the VOBUbuffer 2400 receives the VOBI data on the top of interleave unit ILVU.As a result, the NV extractor 2406 can extracts the data of ILVU_EA andNT_ILVU_SA at the same time with the inputting of navigation pack dataNV, and outputs thereof as signal St2452 (St63) to the decode systemcontroller 2300 (FIG. 26).

[0697] The decode system.controller 2300 stores the signal St2452 intothe ILVU_EA_reg and NT_ILVU_SA_reg, and then start to counts the numberof packs based on the pack terminating signal 2452 from the data counter2408. Based on the fore mentioned the counted value of packs andILVU_EA_reg, the decode system controller 2300 detects the instance whenthe inputting of final pack data of ILVU is completed, or the inputtingfinal byte data of the final pack of the ILVU is completed. Then, thecontroller 2300 further give a command for the bitstream reproducer 2000to move to the position having a sector address indicated byNT_ILVU_SA_reg. The bitstream producer 2000 moves to the sector addressindicated NT_ILVU_SA_reg, and starts to read the data. Thus, thedetection of final end of ILVU and reading process for the next ILVU canbe performed effectively.

[0698] In the above, an example where the multimedia data MBS isreproduced by the bitstream reproducer 2000 without a buffering process,and is inputted to the stream buffer 2499. However, in the case that thesignal processor 2008 of the bitstream reproducer 2000 is incorporatedwith a buffer for error correction process, for example, the controller2300 gives a moving command to reproducer 2000 so that the reproducer2000 moves to the reading position indicated by NT_ILVU_SA_reg aftercompletion of the final pack data of fore mentioned ILVU and clearingthe internal buffer of the reproducer 2000. Thus, the effectivereproduction of ILVU data even when the bitstream reproducer 2000includes a buffer for error correction code (ECC) process.

[0699] Furthermore, when the bitstream producer 2000 has a buffer forECC process, the data can be transferred effectively by providing anymeans having a function equivalent to that of data counter 2408 (FIG.69). In other words, the bitstream reproducer 2000 generates the packinput completion signal St62; the decode system controller 2300 gives acommand based on the signal St62 the bitstream reproducer 200 to move tothe reading position having sector address designated by NT_ILVU_SA_reg.As apparent from the above, the data can be transferred effectively evenwhen the bitstream reproducer 2000 has a function to buffer the datareproduced from the recording media M.

[0700] It is to be noted that the apparatus and method substantially thesame as those described in the above with respect to the interleave unitILVU can be used for the detection VOBU end. In other words, byreplacing the extraction of ILVU_EA and NT_ILVU_Sa, and the storing ofILVU_EA_reg and NT_ILVU_SA_reg with the extraction of VOBU_EA andstoring VOBU_EA_reg, the apparatus and method according to the presentinvention, described above, can be used for the detection of unatend.This is effective for the VOBU data transferring operations shown atsteps #31074, #31082, #31092, and #31102.

[0701] Thus, the reading of data such as ILVU and VOBU can be performedeffectively.

[0702] Decoding Process in the Stream Buffer

[0703] The process for decoding data in the stream buffer 2400 shown asstep #31034 in FIG. 57 is described below referring to FIG. 58. Thisprocess (step #31034) comprises steps #31110, #31112, #31114, and#31116.

[0704] At step #31110 data is transferred in pack units from the streambuffer 2400 to the system decoder 2500 (FIG. 26). The procedure thenmoves to step #31112.

[0705] At step #31112 the pack data is from the stream buffer 2400 toeach of the buffers, i.e., the video buffer 2600, sub-picture buffer2700, and audio buffer 2800.

[0706] At step #31112 the Ids of the user-selected audio and sub-picturedata, i.e., the audio ID AUDIO_ID_reg and the sub-picture ID SP_ID_regstored to the scenario information register shown in FIG. 54, arecompared with the stream ID and sub-stream ID read from the packetheader (FIG. 19), and the matching packets are output to the respectivebuffers. The procedure then moves to step #31114.

[0707] The decode timing of the respective decoders (video, sub-picture,and audio decoders) is controlled in step #31114, i.e., the decodingoperations of the decoders are synchronized, and the procedure moves tostep #31116.

[0708] The respective elementary strings are then decoded at step#31116. The video decoder 3801 thus reads and decodes the data from thevideo buffer, the sub-picture decoder 3100 reads and decodes the datafrom the sub-picture buffer, and the audio decoder 3200 reads anddecodes the data from the audio buffer.

[0709] This stream buffer data decoding process then terminates whenthese decoding processes are completed.

[0710] The decoder synchronization process of step #31114, FIG. 58, isdescribed below with reference to FIG. 59. This processes comprisessteps #31120, #31122, and #31124.

[0711] At step #31120 it is determined whether a seamless connection isspecified between the current cell and the preceding cell. If a seamlessconnection, the procedure moves to step #31122, if not, the proceduremoves to step #31124.

[0712] A process synchronizing operation for producing seamlessconnections is executed in step #31122, and a process synchronizingoperation for non-seamless connections is executed in step #31124.

[0713] To achieve seamless multi-scene reproduction control, it isnecessary to seamlessly reproduce the connections between VOB. Exceptwhen a VOB, which is normally a single-stream title editing unit, isdivided into discrete streams, however, there is no contiguity betweenthe SCR and PTS at the connection. The problems relating to reproducingVOB of which the SCR and PTS are not contiguous are described below.

[0714] Note that the presentation time stamp PTS declaring the videopresentation start time is referenced below as the VPTS, the decodingtime stamp DTS declaring the video decode start time is referenced asVDTS, and the presentation time stamp PTS declaring the audioreproduction, or presentation, start time is referenced as APTS below.

[0715] The relationship between the SCR, APTS, and VPTS values andrecording positions in the VOB are shown in FIG. 47 and described below.For simplification this description is limited to the SCR and PTSparameters. The top SCR value is recorded with the PTS to both themiddle audio stream and bottom video stream. If the positions on thehorizontal axis are approximately the same, approximately the same SCRvalue is recorded to each stream.

[0716] Tse is the time indicated by the SCR of the last pack in the VOB;Tve is the time indicated by the VPTS of the last video pack in the VOB;Tae is the time indicated by the APTS of the last audio pack in the VOB;Tvd is the video decode buffer delay time; and Tad is the audio decodebuffer delay time.

[0717]FIG. 48 is a time line from input of the VOB shown in FIG. 47 tothe system decoder to output of the last audio and video reproductiondata. The horizontal axis shows the passage of time t, and the verticalaxis shows the SCR value, which indicates the time transfer should beaccomplished, and the PTS values, which indicate the time reproductionshould be accomplished.

[0718] Both audio and video outputs are thus delayed by the respectivedecode buffers referenced to the system clock reference SCR, and whilethe audio and video data are input substantially simultaneously, thevideo data is reproduced at a slight delay after the audio data. Thisdelay is caused by the difference in the video and audio decode bufferdelay times.

[0719] In addition, when two VOB are connected, there is no contiguitybetween the SCR and PTS at the connection except when a single-streamVOB is split into separate streams.

[0720] Contiguous reproduction of VOB #1 and VOB #2 havingnon-contiguous SCR and PTS parameters is described below referring toFIG. 46.

[0721]FIG. 46 also shows the relationship between the SCR, APTS, andVPTS values and recording positions in each VOB.

[0722] The system clock reference SCR is time information indicating thepack transfer time, and is recorded with each pack; APTS is the audioplayback starting time information recorded with each audio packet; andVPTS is the video playback starting time information recorded with eachvideo packet. The system clock STC is a reference clock for decodersynchronization control.

[0723] Tse1 is the time indicated by the SCR of the last pack in VOB #1;Tae1 is the time indicated by the last APTS in VOB #1; and Tve1 is thetime indicated by the last VPTS in VOB #1.

[0724] Tad is the audio decode buffer delay time; Tvd is the videodecode buffer delay time; and the horizontal axis indicates the passageof time t.

[0725] What is important to note here is that synchronizing the audioand video so that the reproduced audio and video signals are output atthe time the system clock STC equals the APTS and VPTS values in thestream.

[0726] To maintain the reference clock for transferring VOB to thesystem decoder, the first system clock reference SCR value in VOB #2must be set to the STC initializer at precisely time Tse1. However,because reproduction and output of VOB #1 have not been completed atthis time point, the audio and video still to be output from VOB #1after time Tse1 cannot be normally reproduced because the referenceclock is lost.

[0727] Furthermore, even if the SCR value of the STC initializer is setat the audio end time Tae1, i.e., later than the system clock referenceSCR time Tse1, the reference clock at which the first pack in VOB #2should be transferred is lost, and the reference clock for the VOB #1video output to be reproduced after time Tael is lost.

[0728] The same problem also occurs if the system clock reference SCR isset to the STC initializer at time Tve1.

[0729] When there is a one-to-one correspondence between the VOBreproduced first, i.e., the first VOB, and the VOB reproducedthereafter, i.e., the second VOB, this problem can be avoided byassuring that the first SCR value of the second VOB is contiguous to thelast SCR of the first VOB. However, when common data is shared betweenplural titles, there is a many-to-one relationship between the first VOBand the many VOB that may be reproduced thereafter.

[0730] When contiguously reproducing a second VOB #2 following a firstVOB #1, it is therefore necessary to destroy any remaining VOB #1 datain the decode buffer at time Tse1, and seamless reproduction in whichthe audio and video are not intermitted is not possible.

[0731] A method(s) for seamlessly reproducing VOB of which the SCR andPTS are not contiguous is described by means of the two embodiments ofthe invention below.

[0732] Synchronization Controller: Embodiment 1

[0733] A first embodiment of the synchronizer 2900 shown in FIG. 26 isdescribed according to the present invention with reference to FIG. 32below. As shown in FIG. 32, the synchronizer 2900 comprises a systemclock STC generator 2902, PTS/DTS extractor 2904, video decodersynchronizer 2906, sub-picture decoder synchronizer 2908, audio decodersynchronizer 2910, and system decoder synchronizer 2912.

[0734] The STC generator 2902 generates the system clock for eachdecoder, and supplies the synchronization system clock STC to the videodecoder synchronizer 2906, sub-picture decoder synchronizer 2908, audiodecoder synchronizer 2910, and system decoder synchronizer 2912. The STCgenerator 2902 is described in detail below with reference to FIG. 39.

[0735] The PTS/DTS extractor 2904 extracts the presentation time stampPTS and decoding time stamp DTS from the synchronization control dataSt81, and supplies the PTS and DTS to the decoder synchronizers.

[0736] The video decoder synchronizer 2906 generates the video streamdecoding start signal St89 based on the STC from the STC generator 2902and the decoding time stamp DTS for starting video decoding suppliedfrom the PTS/DTS extractor 2904. More specifically, the video decodersynchronizer 2906 generates the video stream decoding start signal St89when the STC and DTS match.

[0737] The sub-picture decoder synchronizer 2908 generates thesub-picture stream decoding start signal St91 based on the STC from theSTC generator 2902 and the decoding time stamp DTS for startingsub-picture decoding supplied from the PTS/DTS extractor 2904. Morespecifically, the sub-picture decoder synchronizer 2908 generates thesub-picture stream decoding start signal St91 when the STC and DTSmatch.

[0738] The audio decoder synchronizer 2910 generates the audio streamdecoding start signal St93 based on the STC from the STC generator 2902and the decoding time stamp DTS for starting audio decoding suppliedfrom the PTS/DTS extractor 2904. More specifically, the audio decodersynchronizer 2910 generates the audio stream decoding start signal St93when the STC and DTS match.

[0739] The system decoder synchronizer 2912 outputs the STC from the STCgenerator 2902 as the system clock St79. The system clock St79 is usedto control pack transfers from the stream buffers to the system decoder.In other words, if the STC value exceeds the SCR value in the pack, thepack data is transferred from the stream buffer to the system decoder.

[0740] The structure and operation of the STC generator 2902 aredescribed in detail below with reference to FIG. 39. As shown in FIG.39, the STC generator 2902 comprises a system clock STC initializer32010, STC offset calculator 32012, STC counter 32014, STC regenerator32016, STC selection controller 32018, STC selector for video decoder32020, STC selector for sub-picture decoder 32022, STC selector foraudio decoder 32024, and STC selector for system decoder 32026.

[0741] The STC offset calculator 32012 calculates the offset value STCofused to update the system clock STC for contiguous reproduction of twoVOBs with different initial system clock STC values (SCR).

[0742] More specifically, the offset value STCof is calculated bysubtracting the Initial Video Frame Presentation Start TimeVOB_V_SPTM_reg value of the next VOB to be reproduced from the FinalVideo Frame Presentation Termination Time VOB_V_EPTM_reg (see FIG. 39)of the VOB reproduced first.

[0743] The STC counter 32014 is a sequential counter that counts from aset value synchronized to the system clock, and generates the referenceclock STCc for each decoder.

[0744] The STC regenerator 32016 outputs a reset system clock STCr bysubtracting the offset value STCof calculated by the STC offsetcalculator 32012 from the reference clock STCC supplied from the STCcounter 32014.

[0745] The system clock STC initializer 32010 selects and sets the SCRfrom the first pack in the VOB, or the reset system clock STCr outputfrom the STC regenerator 32016, according to the control signal from theSTC selection controller 32018. The value set by the STC initializer32010 is the initial value used by the STC counter 32014.

[0746] The STC selector for video decoder 32020 selects either theoutput STCc from the STC counter 32014 or the output STCr from the STCregenerator 32016 according to the control signal from the STC selectioncontroller 32018, and outputs the selected signal to the video decodersynchronizer 2906.

[0747] The STC selector for sub-picture decoder 32022 similarly selectseither output STCc or output STCr according to the control signal fromthe STC selection controller 32018, and outputs the selected signal tothe sub-picture decoder synchronizer 2908.

[0748] The STC selector for audio decoder 32024 similarly selects eitheroutput STCc or output STCr according to the control signal from the STCselection controller 32018, and outputs the selected signal to the audiodecoder synchronizer 2910.

[0749] The STC selector for system decoder 32026 similarly selectseither output STCc or output STCr according to the control signal fromthe STC selection controller 32018, and outputs the selected signal tothe system decoder synchronizer 2912.

[0750] The operation of the STC selection controller 32018 duringnon-seamless reproduction is described below with reference to FIG. 60.During non-seamless operation (when the SPF_reg flag _SML), all STCselectors, i.e., STC selector for video decoder 32020, STC selector forsub-picture decoder 32022, STC selector for audio decoder 32024, and STCselector for-system decoder 32026, select and output the reference clockSTCc. More specifically, the STC selectors synchronize decoder operationbased on the reference clock STCc output by the STC counter 32014.

[0751] The operation of the STC selection controller 32018 duringseamless reproduction (when the SPF_reg flag=SML) is also describedbelow with reference to FIG. 40 and FIG. 61.

[0752]FIG. 40 also shows the relationship between the SCR, APTS, VDTS,and VPTS values and recording positions in each stream when two VOBs #1and #2 are connected and seamless reproduced.

[0753] The system clock reference SCR is time information indicating thepack transfer time, and is recorded with each pack; APTS is the audioplayback starting time information recorded with each audio packet; VDTSis the video decode start time information recorded with each videopacket; and VPTS is the video playback starting time informationrecorded with each video packet. The system clock STC is a referenceclock for decoder synchronization control.

[0754] Tse1 (Ti) is the time indicated by the SCR of the last pack inVOB #1; Tae1 (T2) is the time indicated by the last APTS in VOB #1; Tde1(T3) is the time indicated by the last VDTS in VOB #1; and Tve1 (T4) isthe time indicated by the last VPTS in VOB #1, i.e., the Final VideoFrame Presentation Termination Time VOB_V_EPTM identified by the lastVPTS in VOB #1.

[0755] Tad is the audio decode buffer delay time; and Tvd is the videodecode buffer delay time.

[0756] Tad is the audio decode buffer delay time; Tdd is the videodecode buffer delay time; and Tve is the sum of the video decode bufferdelay time and the delay until video presentation.

[0757]FIG. 61 is a flow chart used to describe the operation of the STCselection controller 32018 shown in FIG. 39 during seamless reproductionoperation.

[0758] At step #311220, the STC offset (offset value STCof) iscalculated, and the procedure moves to step #311221.

[0759] As described above, the STC offset value STCof is calculated bysubtracting the Initial Video Frame Presentation Start TimeVOB_V_SPTM_reg value of the next VOB to be reproduced from the FinalVideo Frame Presentation Termination Time VOB_V_EPTM_reg (see FIG. 55)of the VOB reproduced first. Thus, the total reproduction time of theVOB reproduced first is calculated as the offset value STCof of the VOBreproduced next.

[0760] At step #311221 the calculated STC offset value STCof is appliedto the STC regenerator 32016 to update the system clock STC. Theprocedure then moves to step #311222.

[0761] The STC regenerator 32016 updates the system clock STC bysubtracting the output STCof from the STC offset calculator 32012 fromthe reference clock STCc output from the STC counter 32014 (STCc-STCof),and outputs the result as the reset system clock STCr.

[0762] At step #311222. the reset system clock STCr is selectivelyoutput by the STC selection controller 32018 to the STC selector forsystem decoder 32026 at time T1 (FIG. 40), i.e., at the time SCR changesfrom stream VOB #1 to VOB #2. The procedure then moves to step #311223.Thereafter the reset system clock STCr is applied as the system clockSTC referenced by the system decoder, and the transfer timing of VOB #2to the system decoder is determined by the SCR in the pack header of thepack and the STCr.

[0763] At step #311223 the reset system clock STCr is selectively outputto the STC selector for audio decoder 32024 at time T2 (FIG. 40), i.e.,at the time APTS changes from stream VOB #1 to VOB #2. The procedurethen moves to step #311224. Thereafter the reset system clock STCr isapplied as the system clock STC referenced by the audio decoder, and theVOB #2 audio output timing is determined by the APTS in the audio packetand the STCr. In other words, when the STCr matches the APTS, the audiodata corresponding to that APTS is reproduced.

[0764] At step #311224 the reset system clock STCr is selectively outputto the STC selector for video decoder 32020 at time T3 (FIG. 40), i.e.,at the time VDTS changes from stream VOB #1 to VOB #2. The procedurethen moves to step #311225. Thereafter the reset system clock STCr isapplied as the system clock STC referenced by the video decoder, and theVOB #2 video decode timing is determined by the VDTS in the video packetand the STCr. In other words, when the STCr matches the VDTS, the videodata corresponding to that VDTS is decoded.

[0765] At step #311225 the reset system clock STCr is selectively outputto the STC selector for sub-picture decoder 32022 at time T4 (FIG. 40),i.e., at the time VPTS changes from stream VOB #1 to VOB #2. Theprocedure then moves to step #311226. Thereafter the reset system clockSTCr is applied as the system clock STC referenced by the sub-picturedecoder, and the VOB #2 sub-picture presentation timing is determined bythe presentation time stamp PTS in the sub-picture packet and the STCr.

[0766] In other words, when the STCr matches the PTS, the sub-picturedata corresponding to that PTS is reproduced. Note that the process fromsub-picture decoding to presentation is accomplished instantaneously. Asa result, the system clock STC value referenced by the sub-picturedecoder changes at the same timing at which the video playback startingtime information VPTS changes from VOB #1 to VOB #2.

[0767] At step #311226 the STCr is reset to the STC initializer 32010.The STC initializer 32010 thus supplies this updated clock to the STCcounter 32014, which operates using this reset system clock STCr valueas the initial value. The procedure then moves to step #311227.

[0768] At step #311227 all of the STC selectors, i.e., STC selector forvideo decoder 32020, STC selector for sub-picture decoder 32022, STCselector for audio decoder 32024, and STC selector for system decoder32026, output the reference clock STcc.

[0769] Thereafter, the system clock STC referenced by the video decoder,sub-picture decoder, audio decoder, and system decoder is the referenceclock STCc output from the STC counter 32014.

[0770] The process from step #311226 to step #311227 must only beaccomplished by the time the system clock reference SCR changes from theVOB #2 SCR to the first SCR in the VOB following VOB #2, i.e., by timeT1 at which the change to the next VOB is accomplished.

[0771] Note that the STC switching time T1 can also be obtained bydetecting the change in the Initial Video Frame Presentation Start TimeVOB_V_SPTM or the Final Video Frame Presentation Termination TimeVOB_V_EPTM in the navigation pack NV, and extracting the SCR in the packimmediately before the change. Note that the same VOB_V_SPTM andVOB_V_EPTM values are recorded to all navigation packs NV in the sameVOB. As a result, when either of these values changes, the VOB has alsochanged, and by monitoring a change in either of these values, it ispossible to know that the VOB has changed.

[0772] T1 can be obtained by adding the pack transfer time to the SCRvalue in the pack immediately before the VOB changed. Note that the packtransfer time is a constant value.

[0773] STC switching times T2 and T3 can also be calculated from theAPTS, VDTS, and VPTS values extracted immediately before the VOB_V_SPTMor VOB_V_EPTM value in the navigation pack NV changes.

[0774] T2 is calculated by extracting the APTS from the audio packetimmediately before the VOB changes, and adding the audio reproductiontime contained in the audio packet of the corresponding APTS value. Notethat the audio reproduction time contained in the audio packet can becalculated from the audio bit rate and the packet data size.

[0775] T3 can be obtained by extracting the VDTS from the video packetcontaining the corresponding VDTS immediately before the VOB changes. T3is thus obtained as the time defined by the VDTS.

[0776] T4 is equivalent to the VOB_V_EPTM value, which is thereforeused.

[0777] Synchronization Controller: Embodiment 2

[0778] A second embodiment of the synchronizer 2900 shown in FIG. 26 isdescribed according to the present invention with reference to FIG. 41below. As shown in FIG. 41, the synchronizer 2900 comprises a systemclock STC generator 32030, PTS/DTS extractor 32031, synchronizationcontroller 32032, video decoder synchronizer 32033, sub-picture decodersynchronizer 32034, audio decoder synchronizer 32035, and system decodersynchronizer 32036.

[0779] The STC generator 32030 generates the system clock for eachdecoder, and supplies the synchronization system clock STC to the videodecoder synchronizer 32033, sub-picture decoder synchronizer 32034,audio decoder synchronizer 32035, and system decoder synchronizer 32036.The STC generator 32030 is a counter that operates at the system clock.The SCR from the first pack in the first VOB in the program chain PGC isset as the initial counter value, and is thereafter-incremented based onthe system clock. Note that the initial STC counter value may be resetto the APTS or VPTS value.

[0780] Both the audio and video outputs are reproduced synchronized tothe respective output clocks. It is therefore possible forsynchronization to be disrupted by the accumulated error in STC, audiooutput clock, and video output clock precision. When this accumulatederror becomes great, the respective decoder buffers may be destroyed (bya data underflow or overflow state). Therefore, by periodicallyresetting the system clock STC to the APTS synchronized to the audiooutput clock, for example, APTS-STC error accumulation can be prevented,and the audio can be reproduced without interruption. In this case,video synchronization is controlled by skipping or freezing videooutput.

[0781] This type of synchronization control is defined as Audio Mastersynchronization control.

[0782] On the other hand, by periodically resetting the system clock STCto the VPTS synchronized to the video output clock, VPTS-STC erroraccumulation can be prevented, and the video can be seamlesslyreproduced. In this case, audio synchronization is controlled byskipping or pausing audio output.

[0783] This type of synchronization control is defined as Video Mastersynchronization control.

[0784] In the following description of synchronization control, an ONsynchronization mode refers to STC-referenced synchronization control,either Audio or Video Master. An OFF synchronization mode is whenSTC-referenced synchronization control is not applied. In an OFFsynchronization mode the audio and video decoders sequentially outputthe audio and video at a defined frame frequency based on the respectiveinternal reference clocks without referencing the time stamp values fromthe streams, and no timing control is applied to synchronize the audioand video.

[0785] The PTS/DTS extractor 32031 extracts the presentation time stampPTS and decoding time stamp DTS from the synchronization control dataSt81, and supplies the PTS and DTS to the respective decodersynchronizers.

[0786] The synchronization controller 32032 generates thesynchronization control signal specifying an ON or OFF synchronizationmode for each of the decoder synchronizers. This synchronizationcontroller 32032 is described in detail below with reference to FIG. 42.

[0787] If the synchronization control signal from the synchronizationcontroller 32032 specifies an ON synchronization mode, the video decodersynchronizer 32033 generates the video stream decoding start signal St89based on the STC from the STC generator 32030 and the decoding timestamp DTS for starting video decoding supplied from the PTS/DTSextractor 32031. More specifically, the video decoder synchronizer 32033generates the video stream decoding start signal St89 when the STC andDTS match.

[0788] If the synchronization control signal from the synchronizationcontroller 32032 specifies an OFF synchronization mode, the videodecoder synchronizer 32033 constantly outputs the video streamdecoding.start signal St89. Thus, the video decoder operatesindependently of external control, and is controlled by internal stateinformation.

[0789] If the synchronization control signal from the synchronizationcontroller 32032 specifies an ON synchronization mode, the sub-picturedecoder synchronizer 32034 generates the sub-picture stream decodingstart signal St91 based on the STC from the STC generator 32030 and thedecoding time stamp DTS for starting sub-picture decoding supplied fromthe PTS/DTS extractor 32031. More specifically, the sub-picture decodersynchronizer 32034 generates the sub-picture stream decoding startsignal St91 when the STC and DTS match.

[0790] If the synchronization control signal from the synchronizationcontroller 32032 specifies an OFF synchronization mode, the sub-picturedecoder synchronizer 32034 constantly outputs the sub-picture streamdecoding start signal St91. Thus, the sub-picture decoder operatesindependently of external control, and is controlled by internal stateinformation.

[0791] If the synchronization control signal from the synchronizationcontroller 32032 specifies an ON synchronization mode, the audio decodersynchronizer 32035 generates the audio stream decoding start signal St93based on the STC from the STC generator 32030 and the decoding timestamp DTS for starting audio decoding supplied from the PTS/DTSextractor 32031. More specifically, the audio decoder synchronizer 32035generates the audio stream decoding start signal St93 when the STC andDTS match.

[0792] If the synchronization control signal from the synchronizationcontroller 32032 specifies an OFF synchronization mode, the audiodecoder synchronizer 32035 constantly outputs the audio stream decodingstart signal St93. Thus, the audio decoder operates independently ofexternal control, and is controlled by internal state information.

[0793] The system decoder synchronizer 32036 outputs the STC from theSTC generator 32030 as the system clock St79. The system clock St79 isused to control pack transfers from the stream buffers to the systemdecoder. In other words, if the STC value matches the SCR value in thepack, the pack data is transferred from the stream buffer to the systemdecoder.

[0794] The structure and operation of the synchronization controller32032 are described below with reference to FIG. 42 and FIG. 43.

[0795] The structure of the synchronization controller 32032 is shown inFIG. 42. As shown in the figure, the synchronization controller 32032comprises an SCR change detector 32040, APTS changing time detector32041, VPTS changing time detector 32042, and synchronization modeselector 32043.

[0796] The SCR change detector 32040 generates and supplies to thesynchronization mode selector 32043 an ACTIVE SCR change detectionsignal if the SCR value in the pack header in the synchronizationcontrol data St81 changes to 0. By thus setting the SCR to 0 in thefirst pack of the VOB reproduced later when seamlessly connecting andreproducing two VOB, the VOB break point can be easily detected. Notethat the SCR is not set to 0 when an originally contiguous VOB isdivided in two, i.e., when the SCR is contiguous between two VOB.

[0797] Note, further, that while a 0 value is described here, any valuewhereby the beginning and end of each VOB can be easily determined canbe used.

[0798] In the case of parental lock control, for example, when a singlestream, e.g., VOB #2, is reconnected to one of plural possible scenes,e.g., VOB #1, from the multi-scene period enabling parental lockcontrol, each of the VOB in the multi-scene period may have a differentreproduction time, and it is not possible to assign the first SCR valuein each possible VOB #2 to account for all possible connections. Aseamless can be achieved in such cases, however, by setting the SCR ofthe first pack in VOB #2 to 0.

[0799] The APTS changing time detector 32041 compares the APTS in thesynchronization control data St81 when the VOB changes with the STCcounter value supplied from the STC generator 32030 shown in FIG. 41.When the STC counter exceeds the APTS, the APTS changing time detector32041 generates and inputs to the synchronization mode selector 32043 anACTIVE APTS change time detection signal.

[0800] Note that the method of detecting the APTS when the VOB changesis described below with reference to FIG. 43.

[0801] The VPTS changing time detector 32042 compares the VPTS in thesynchronization control data St81 when the VOB changes with the STCcounter value supplied from the STC generator 32030. When the STCcounter exceeds the VPTS, the VPTS changing time detector 32042generates and inputs to the synchronization mode selector 32043 anACTIVE VPTS change time detection signal.

[0802] Note that the method of detecting the VPTS when the VOB changesis described below with reference to FIG. 43.

[0803] Based on the SCR change detection signal from the SCR changedetector 32040, the APTS change time detection signal from the APTSchanging time detector 32041, and the VPTS change time detection signalfrom the VPTS changing time detector 32042, the synchronization modeselector 32043 generates the synchronization mode selection signals, andoutputs to the video decoder synchronizer 32033, sub-picture decodersynchronizer 32034, audio decoder synchronizer 32035, and system decodersynchronizer 32036. The STC update signal STCs is also output to the STCgenerator 32030.

[0804] The respective decoder synchronizers control synchronizationbased on the system clock STC if an ON synchronization mode isspecified. If an OFF synchronization mode is specified, the STC is notused for synchronization control as described above.

[0805] The operation of the synchronization mode selector 32043 isdescribed next with reference to FIG. 43.

[0806] At step #320430 the STC update signal STCs is generated andoutput to the STC generator 32030, and the procedure moves to step#320431. If the STC update signal STCs is ACTIVE, the STC generator32030 sets a new SCR from the synchronization control data St81 as theinitial value, and updates the STC.

[0807] At step #320431 the synchronization mode selector 32043 outputs asynchronization mode selection signal specifying an ON synchronizationmode to the decoder synchronizers 32033, 32034, 32035, and 32036. Theprocedure then moves to step #320432.

[0808] At step #320432 the procedure moves to step #320433 if the SCRchange detector 32040 detects that the SCR has changed. If an SCR changeis not detected, this step is repeated until an SCR change is detected.As a result, an ON synchronization mode continues to be output to thedecoder synchronizers as long as this step executes.

[0809] At step #320433 the synchronization mode selector 32043 outputs asynchronization mode selection signal specifying an OFF synchronizationmode to the decoder synchronizers 32033, 32034, 32035, and 32036. Theprocedure then moves to step #320434. This step thus means that thesynchronization mode is OFF from the time T1 the VOB changed during packtransfer.

[0810] If both the APTS changing time detector 32041 and VPTS changingtime detector 32042 detect a changed time at step #320434, control loopsback to step #320430, and the synchronization mode is set ON again atstep #320431. However, if a changed time is not detected, step #320434repeats until both the APTS and VPTS are detected to change. This stepthus means that the decoder synchronizers continue operating in an OFFsynchronization mode.

[0811] Synchronization control at the start of normal reproduction,i.e., at a VOB start without contiguous reproduction from a precedingVOB, is described next with reference to FIG. 44.

[0812]FIG. 44 shows the relationship between the system clock referenceSCR indicating the time a VOB is input to the system decoder data, theaudio playback starting time information APTS, the decoder referenceclock STC, and the video playback starting time VPTS, referenced to timeshown on the horizontal axis with the values expressed in terms of thepresentation start time PST on the vertical axis.

[0813] The point at which the first SCR in the VOB is 0 is point A. Ifthe first SCR is not 0, e.g., if normal reproduction is resumed from themiddle of a VOB after a special reproduction mode, the control procedureis the same. The times between input and output of the audio data andvideo data, respectively, to and from the system decoder are expressedas DTad and DTvd. Because DTad<DTvd, and data is recorded at the VOBbeginning referenced to the time it is reproduced, only video data ispresent at point C at the VOB start, and the audio data is recorded atpoint D after a delay of DTvd-DTad.

[0814] Synchronization is controlled at this point as described below.Video and audio output is first stopped, the SCR value from the pack atpoint A is set to the STC generator 32030, and the STC generator 32030operates an internal counter at the system clock and outputs the systemclock STC. Transfer of the first pack in the VOB to the system decoder2500 starts at the same time. The following packs are transferred at theSCR recorded in the pack header of each pack referenced to the systemclock STC produced by the STC generator 32030.

[0815] The first video data is then decoded, and video output starts atpoint F when the STC output from the STC generator 32030 matches thefirst VPTS value.

[0816] Audio output is similarly controlled: the first audio data isdecoded, and audio output starts at point E, the moment when the STCoutput from the STC generator 32030 matches the first APTS value.

[0817] After reproduction of the start of the VOB thus begins, the audioAPTS value is periodically set to the STC generator 32030 to controlsynchronization under Audio Master or Video Master control.

[0818] The method of synchronizing seamless reproduction of two VOB isdescribed next. The detection method of the SCR change detector 32040,APTS changing time detector 32041, and VPTS changing time detector 32042in FIG. 42 is particularly described with reference to FIG. 45.

[0819]FIG. 45 shows the relationship between the recording positions andvalues of SCR, APTS, and VPTS when VOB #1 and VOB #2 are seamlesslyreproduced. Why the synchronization mode of the decoder synchronizersmust be switched ON and OFF to achieve seamless reproduction isdescribed first.

[0820] Point G is the time at which the pack being transferred changesfrom VOB #1 to VOB #2, H is the time the audio output changes, and I isthe time the video output changes. Because the audio output and videooutput thus change at different times, synchronization control cannot beachieved using a single system clock STC. It is therefore necessary toprevent synchronization control using the STC during the period fromwhen the SCR changes at time G to when both the APTS and VPTS havechanged at time I. After both the APTS and VPTS have changed at time I,synchronization control using the STC is again possible and necessary.

[0821] The method of detecting the timing at which synchronizationcontrol is stopped, i.e., when the synchronization mode is turned OFF,is described next.

[0822] The timing at which the synchronization mode is turned OFF isobtained from the SCR time chart in FIG. 45. VOB #1 is being output tothe system decoder while the SCR value increases, and SCR becomes 0 onlyat time G, i.e., when VOB #1 transfer stops and VOB #2 transfer begins.Therefore, by detecting the time at which the SCR value becomes 0, it isknown that VOB #2 is being input to the system decoder, and thesynchronization mode is therefore set OFF at this time Tg.

[0823] It is also possible to detect that the SCR is 0 when the value iswritten to the stream buffer. The synchronization mode can also be setOFF when a 0 SCR value is detected written to the stream buffer.

[0824] The timing at which synchronization control begins, i.e., whenthe synchronization mode is turned from OFF to ON, is described next.

[0825] To start synchronization control it is necessary to know whenboth the audio and video output have switched from VOB #1 to VOB #2. Themoment when the audio output changes to VOB #2 can be known by detectingthe point H at which the APTS value stops increasing. Likewise, themoment when the video output changes to VOB #2 can be known by detectingthe point I at which the VPTS value stops increasing. After both pointsH and I have appeared, the synchronization mode is immediately set ON attime Ti.

[0826] The timing at which the synchronization mode is set OFF can alsobe delayed to a time between time Tg and time Ti, rather than at time Tgwhen an SCR change is detected. By setting the synchronization mode OFFat time Th, i.e., the time at which a change in APTS or VPTS isdetected, between Tg and Ti, the duration of the OFF synchronizationmode can be shortened.

[0827] However, when the timing is based on detecting whether both APTSand VPTS values continue increasing, it is clear that both APTS and VPTSvalues must decrease when VOB are connected. In other words, the lastAPTS and VPTS values in a VOB must be greater than the maximum initialAPTS and VPTS values in a VOB.

[0828] The maximum initial (DTad and DTvd) APTS and VPTS values aredefined as follows.

[0829] The initial APTS and VPTS values are the sums of the video dataand audio data storage times in the video and audio buffers, and thevideo reordering time (in MPEG. video, the picture decode order andpresentation order are not necessarily the same, and presentation isdelayed a maximum one picture from the decoder). Therefore, the sum ofthe time required for the video buffer and audio buffer to fill, and thepresentation delay (1 frame period) from video reordering, determinesthe maximum initial values for APTS and VPTS.

[0830] As a result, the last APTS and VPTS values in a VOB are alwaysassigned to exceed these maximum initial values when the VOB areproduced.

[0831] While it is possible to control the timing at which thesynchronization mode is turned ON following VOB connection by detectingwhether both APTS and VPTS values continue increasing, it is alsopossible to achieve the same synchronization control by detecting thetime at which the APTS value drops below an APTS threshold value, andthe VPTS value drops below an VPTS threshold value.

[0832] These APTS and VPTS threshold values can be calculated by usingvalues equal to the maximum initial APTS and VPTS values of the VOB asthe threshold values, and calculating them as described above.

[0833] By applying ON/OFF synchronization mode control as describedabove, seamless reproduction that does not disturb the playbackcondition can be achieved in VOB connections.

[0834] Note that various methods can be used in the reproductionapparatus for audio and video synchronization control in the secondembodiment described above. The most common of these methods (1) is toreset the system clock. STC to the APTS value every few seconds,determine whether the VPTS value is fast or slow referenced to thesystem clock STC, and freeze or skip video output as necessary. This isthe so-called Audio Master method described above.

[0835] Alternatively, it is also possible (2) to reset the system clockSTC to the VPTS value every few seconds, determine whether the APTSvalue is fast or slow referenced to the system clock STC, and freeze orskip audio output as necessary. This is the so-called Video Mastermethod described above.

[0836] Another method (3) is to directly compare the APTS and VPTSvalues, and use either the APTS or VPTS value for reference.

[0837] Regardless of which method is used for ON/OFF synchronizationmode control, however, the same effect can be achieved.

[0838] As described above, two methods are used for audio-videosynchronization according to the present embodiment, Audio Master andVideo Master synchronization control. For Audio Master synchronizationcontrol the system clock STC is periodically reset to the APTS value,whether the VPTS value is earlier or later is determined referenced tothe reset system clock STC, and the video presentation is frozen orskipped as necessary for synchronization. For Video Mastersynchronization control the system clock STC is periodically reset tothe VPTS value, whether the APTS value is earlier or later is determinedreferenced to the reset system clock STC, and the audio presentation ispaused or skipped as necessary for synchronization. It is also possibleto.directly compare the APTS and VPTS values, and controlsynchronization referenced to either the APTS or VPTS value. Regardlessof which method is used for AV synchronization control, however, thesame effects can be obtained.

[0839] Furthermore, while the above embodiments have been describedusing an initial VOB SCR value of 0, a value other than 0 can be usedand the same control achieved by adding the first SCR value as an offsetvalue to the APTS and VPTS values.

[0840] It is also possible in the second embodiment above to read theSTC discontinuity flag STCDCF_reg, which specifies whether the next cellreproduced needs the STC to be reset. If the register reads STC_NRESET,the synchronization mode is constantly ON; if STC_RESET is stored,ON/OFF synchronization mode control can be applied.

[0841] It is thus possible to decode the data transferred to the streambuffer 2400 while synchronizing the operation of the various decoders.

[0842] It is therefore possible by means of the present invention thusdescribed to maintain synchronization between the audio and video data,and seamlessly connect and reproduce two VOB during reproduction from amulti-scene period even when there is no continuity between the systemclock reference SCR and presentation time stamp PTS values used forsynchronization control of the VOB to be contiguously reproduced.

[0843] Although the present invention has been fully described inconnection with the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. A data stream reproduction apparatus forreproducing data streams, the data streams including sub-picture datastreams including a plurality of sub-picture data units, the sub-picturedata units being respectively associated with first time codes operableto indicate transfer timings at which the respective sub-picture dataunits are input to a buffer, at least one sub-picture data unit beingassociated with a second time code operable to indicate a sub-picturedecoding timing at which the at least one sub-picture data unit isdecoded, said apparatus comprising: a decoder, which includes a buffer,operable to store the sub-picture data streams input thereto and thendecode the stored sub-picture data streams with reference to a referenceclock, so as to decode the stored sub-picture data streams at thesub-picture decoding timing based on the second time code; a sub-picturedata stream supplying arrangement operable to supply the sub-picturedata streams to the buffer with reference to the reference clock so asto input the sub-picture data units at the transfer timings based on thefirst time codes, respectively; and a controller operable to supply thereference clock to said decoder and said sub-picture data streamsupplying arrangement; wherein said controller comprises: a system clockgenerator operable to generate a first clock and a second clockdifferent from the first clock; and a system clock selector operable toselectively output the first and second clocks in such a manner that,during a first period, one of the first and second clocks is supplied asthe reference clock both to said sub-picture data stream supplyingarrangement and said decoder and, during a second period, one of thefirst and second clocks is supplied to said sub-picture data streamsupplying arrangement while the other of the first and second clocks issupplied to said decoder.
 2. A data stream reproduction apparatusaccording to claim 1, wherein the sub-picture data streams include afirst sub-picture data stream and a second sub-picture data streamfollowing the first sub-picture data stream, and wherein the firstperiod terminates after a last sub-picture data unit of the firstsub-picture data stream is supplied to the buffer of the decoder, whilethe second period follows the first period and terminates after the lastsub-picture data unit of the first sub-picture data stream isreproduced.
 3. An optical disk for use with a data stream reproductionapparatus, the data stream reproduction apparatus is for reproducingdata streams, the data streams including sub-picture data streamsincluding a plurality of sub-picture data units, the sub-picture dataunits being respectively associated with first time codes operable toindicate transfer timings at which the respective sub-picture data unitsare input to a buffer, at least one sub-picture data unit beingassociated with a second time code operable to indicate a sub-picturedecoding timing at which the at least one sub-picture data unit isdecoded, the apparatus including: a decoder, which includes a buffer,operable to store the sub-picture data streams input thereto and thendecode the stored sub-picture data streams with reference to a referenceclock, so as to decode the stored sub-picture data streams at thesub-picture decoding timing based on the second time code; a sub-picturedata stream supplying arrangement operable to supply the sub-picturedata streams to the buffer with reference to the reference clock so asto input the sub-picture data units at the transfer timings based on thefirst time codes, respectively; and a controller operable to supply thereference clock to the decoder and the sub-picture data stream supplyingarrangement; wherein the controller comprises: a system clock generatoroperable to generate a first clock and a second clock different from thefirst clock; and a system clock selector operable to selectively outputthe first and second clocks in such a manner that, during a firstperiod, one of the first and second clocks is supplied as the referenceclock both to the sub-picture data stream supplying arrangement and thedecoder and, during a second period, one of the first and second clocksis supplied to the sub-picture data stream supplying arrangement whilethe other of the first and second clocks is supplied to the decoder;said optical disk comprising: a data region operable to store the datastreams including first data stream including first sub-picture datastream and second data stream including second sub-picture data stream;and a management information region operable to store connectioninformation which is utilized during data stream reproduction andindicates that the first data stream is followed by the second data;wherein the connection information includes system clock selectioninformation for use during data stream reproduction so that the firstdata stream is supplied to the buffer and then decoded with reference toone of the first and second clocks while the second data stream issupplied to the buffer and then decoded with reference to the other ofthe first and second clocks.
 4. An optical disk according to claim 3,wherein the first period terminates after a last sub-picture data unitof the first sub-picture data stream is supplied to the buffer of thedecoder, while the second period follows the first period and terminatesafter the last sub-picture data unit of the first sub-picture datastream is reproduced.
 5. A data stream reproduction method forreproducing data streams, the data streams including sub-picture datastreams including a plurality of data units, the sub-picture data unitsbeing respectively associated with first time codes operable to indicatetransfer timings at which the respective sub-picture data units areinput to a buffer, at least one sub-picture data unit being associatedwith a second time code operable to indicate a sub-picture decodingtiming at which the at least one sub-picture data unit is decoded, saidmethod comprising: storing the sub-picture data streams in a decoder,which includes a buffer, and then decoding the stored sub-picture datastreams with reference to a reference clock, so as to decode the storedsub-picture data streams at the subpicture decoding timing based on thesecond time code; supplying the sub-picture data streams to the buffervia a sub-picture data stream supplying arrangement with reference tothe reference clock so as to input the sub-picture data units at thetransfer timings based on the first time codes, respectively; andsupplying the reference clock to the decoder and the sub-picture datastream supplying arrangement; wherein said supplying the reference clockincludes: generating a first clock and a second clock different from thefirst clock; and selectively outputting the first and second clocks insuch a manner that, during a first period, one of the first and secondclocks is supplied as the reference clock both to the sub-picture datastream supplying arrangement and the decoder and, during a secondperiod, one of the first and second clocks is supplied to thesub-picture data stream supplying arrangement while the other of thefirst and second clocks is supplied to the decoder.
 6. A data streamreproduction method according to claim 5, wherein the sub-picture datastreams include a first sub-picture data stream and a second subpicturedata stream following the first sub-picture data stream, and wherein thefirst period terminates after a last sub-picture data unit of the firstsub-picture data stream is supplied to the buffer of the decoder, whilethe second period follows the first period and terminates after the lastsub-picture data unit of the first sub-picture data stream isreproduced.